NB. This post has rec'd over 7,200 hits. Just to be clear: I did not research/compose this list. I cribbed it from Wikipedia. There's a link to the Wiki article at the bottom of the post.
It's a shame that being stupid doesn't actually hurt. . .
- José de Acosta (1539–1600) – Jesuit missionary and naturalist who wrote one of the very first detailed and realistic descriptions of the new world
- François d'Aguilon (1567–1617) – Belgian Jesuit mathematician, physicist, and architect.
- Lorenzo Albacete (1941) Priest physicist and theologian
- Albert of Saxony (philosopher) (c. 1320–1390) – German bishop known for his contributions to logic and physics; with Buridan he helped develop the theory that was a precursor to the modern theory of inertia
- Albertus Magnus (c. 1206–1280) – Dominican friar and Bishop of Regensberg who has been described as "one of the most famous precursors of modern science in the High Middle Ages." Patron saint of natural sciences; Works in physics, logic, metaphysics, biology, and psychology.
- Giulio Alenio (1582-1649) - Jesuit theologian, astronomer and mathematician. He was sent to the Far East as a missionary and adopted a Chinese name and customs. He wrote 25 books including a cosmography and a Life of Jesus in Chinese.
- José María Algué (1856–1930) – Priest and meteorologist who invented the barocyclonometer
- José Antonio de Alzate y Ramírez (1737–1799) – Priest, scientist, historian, cartographer, and meteorologist who wrote more than thirty treatises on a variety of scientific subjects
- Francesco Castracane degli Antelminelli (1817–1899) – Priest and botanist who was one of the first to introduce microphotography into the study of biology
- Giovanni Antonelli (1818–1872) – Priest and director of the Ximenian Observatory of Florence who also collaborated on the design of a prototype of the internal combustion engine
- Nicolò Arrighetti (1709–1767) – Jesuit who wrote treatises on light, heat, and electricity.
- Giuseppe Asclepi (1706–1776) – Jesuit astronomer and physician who served as director of the Collegio Romano observatory; The lunar crater Asclepi is named after him.
- Roger Bacon (c. 1214–1294) – Franciscan friar who made significant contributions to mathematics and optics and has been described as a forerunner of modern scientific method.
- Bernardino Baldi (1533–1617) – Abbot, mathematician, and writer
- Eugenio Barsanti (1821–1864) – Piarist who is the possible inventor of the internal combustion engine
- Bartholomeus Amicus (1562–1649) – Jesuit wrote on philosophy, mathematics, astronomy, and the concept of vacuum and its relationship with God.
- Daniello Bartoli (1608–1685) – Bartoli and fellow Jesuit astronomer Niccolò Zucchi are credited as probably having been the first to see the equatorial belts on the planet Jupiter
- Joseph Bayma (1816–1892) – Jesuit known for work in stereochemistry and mathematics
- Giacopo Belgrado (1704–1789) – Jesuit professor of mathematics and physics and court mathematician who did experimental work in physics
- Mario Bettinus (1582–1657) – Jesuit philosopher, mathematician and astronomer; lunar crater Bettinus named after him
- Giuseppe Biancani (1566–1624) – Jesuit astronomer, mathematician, and selenographer, after whom the crater Blancanus on the Moon is named
- Jacques de Billy (1602–1679) – Jesuit who has produced a number of results in number theory which have been named after him; published several astronomical tables; The crater Billy on the Moon is named after him.
- Paolo Boccone (1633–1704) – Cistercian botanist who contributed to the fields of medicine and toxicology
- Bernard Bolzano (1781–1848) – Priest, mathematician, and logician whose other interests included metaphysics, ideas, sensation, and truth.
- Anselmus de Boodt (1550–1632) – Canon who was one of the founders of mineralogy
- Theodoric Borgognoni (1205–1298) – Dominican friar, Bishop of Cervia, and medieval Surgeon who made important contributions to antiseptic practice and anaesthetics
- Christopher Borrus (1583–1632) – Jesuit mathematician and astronomy who made observations on the magnetic variation of the compass
- Roger Joseph Boscovich (1711–1787) – Jesuit polymath known for his contributions to modern atomic theory and astronomy
- Joachim Bouvet (1656–1730) – Jesuit sinologist and cartographer who did his work in China
- Michał Boym (c. 1612–1659) – Jesuit who was one of the first westerners to travel within the Chinese mainland, and the author of numerous works on Asian fauna, flora and geography.
- Thomas Bradwardine (c. 1290–1349) – Archbishop of Canturbury and mathematician who helped develop the mean speed theorem; one of the Oxford Calculators
- Martin Stanislaus Brennan (1845-1927) - Priest and astronomer who wrote several books about science
- Henri Breuil (1877–1961) – Priest, archaeologist, anthropologist, ethnologist and geologist.
- Jan Brożek (1585–1652) – Polish canon, polymath, mathematician, astronomer, and physician; the most prominent Polish mathematician of the 17th century
- Louis-Ovide Brunet (1826–1876) – Priest who was one of the founding fathers of Canadian botany
- Francesco Faà di Bruno (c. 1825–1888) – Priest and mathematician beatified by Pope John Paul II
- Ismaël Bullialdus (1605–1694) – Priest, astronomer, and member of the Royal Society; the Bullialdus crater is named in his honor
- Jean Buridan (c. 1300 – after 1358) – Priest who formulated early ideas of momentum and inertial motion and sowed the seeds of the Copernican revolution in Europe
- Roberto Busa (1913-2011) - Jesuit wrote a lemmatization of the complete works of St. Thomas Aquinas (Index Thomisticus) which was later digitalized by IBM.
- Niccolò Cabeo (1586–1650) – Jesuit mathematician; the crater Cabeus is named in his honor
- Nicholas Callan (1799–1846) – Priest & Irish scientist best known for his work on the induction coil
- Jean Baptiste Carnoy (1836–1899) – Priest who has been called the founder of the science of cytology[by whom?]
- Giovanni di Casali (died c. 1375) – Franciscan friar who provided a graphical analysis of the motion of accelerated bodies
- Paolo Casati (1617–1707) – Jesuit mathematician who wrote on astronomy and vacuums; The crater Casatus on the Moon is named after him.
- Laurent Cassegrain (1629–1693) – Priest who was the probable namesake of the Cassegrain telescope; The crater Cassegrain on the Moon is named after him
- Benedetto Castelli (1578–1643) – Benedictine mathematician; long-time friend and supporter of Galileo Galilei, who was his teacher; wrote an important work on fluids in motion
- Bonaventura Cavalieri (1598–1647) – Jesuate known for his work on the problems of optics and motion, work on the precursors of infinitesimal calculus, and the introduction of logarithms to Italy. Cavalieri's principle in geometry partially anticipated integral calculus; the lunar crater Cavalerius is named in his honor
- Antonio José Cavanilles (1745–1804) – Priest and leading Spanish taxonomic botanist of the 18th century
- Francesco Cetti (1726–1778) – Jesuit zoologist and mathematician
- Tommaso Ceva (1648–1737) – Jesuit mathematician and professor who wrote treatises on geometry, gravity, and arithmetic
- Christopher Clavius (1538–1612) – Respected Jesuit Astronomer and mathematician who headed the commission that yielded the Gregorian calendar; wrote influential astronomical textbook.
- Guy Consolmagno (1952– ) – Jesuit astronomer and planetary scientist
- Nicolaus Copernicus (1473–1543) –Renaissance astronomer and canon famous for his heliocentric cosmology that set in motion the Copernican Revolution
- Vincenzo Coronelli (1650–1718) – Franciscan cosmographer, cartographer, encyclopedist, and globe-maker
- George Coyne (1933– ) – Jesuit astronomer and former director of the Vatican Observatory
- James Cullen (mathematician) (1867–1933) – Jesuit mathematician who published what is now known as Cullen numbers in number theory
- James Curley (astronomer) (1796–1889) – Jesuit who was the first director of Georgetown Observatory and determined the latitude and longitude of Washington D.C.
- Albert Curtz (1600–1671) – Jesuit astronomer who expanded on the works of Tycho Brahe and contributed to early understanding of the moon; The crater Curtius on the Moon is named after him.
- Johann Baptist Cysat (1587–1657) – Jesuit mathematician and astronomer, after whom the lunar crater Cysatus is named; published the first printed European book concerning Japan; one of the first to make use of the newly developed telescope; most important work was on comets
- Jean-Baptiste Chappe d'Auteroche (1722-1769) - Priest and astronomer best known for his observations of the transits of Venus
- Ignazio Danti (1536–1586) – Dominican mathematician, astronomer, cosmographer, and cartographer
- Armand David (1826–1900) – Lazarist priest, zoologist, and botanist who did important work in these fields in China
- Francesco Denza (1834–1894) – Barnabite meteorologist, astronomer, and director of Vatican Observatory
- Václav Prokop Diviš (1698–1765) – Czech priest who studied the lightning rod independent of Franklin and constructed the first electrified musical instrument in history
- Johann Dzierzon (1811–1906) – Priest and pioneering apiarist who discovered the phenomenon of parthenogenesis among bees, and designed the first successful movable-frame beehive; has been described as the "father of modern apiculture"
- Francesco Faà di Bruno (c. 1825–1888) – Priest and mathematician beatified by Pope John Paul II
- Honoré Fabri (1607–1688) – Jesuit mathematician and physicist
- Jean-Charles de la Faille (1597–1652) – Jesuit mathematician who determined the center of gravity of the sector of a circle for the first time
- Gabriele Falloppio (1523–1562) – Canon and one of the most important anatomists and physicians of the sixteenth century. The Fallopian tubes, which extend from the uterus to the ovaries, are named for him.
- Gyula Fényi (1845–1927) – Jesuit astronomer and director of the Haynald Observatory; noted for his observations of the sun; The crater Fényi on the Moon is named after him
- Louis Feuillée (1660–1732) – Minim explorer, astronomer, geographer, and botanist
- Placidus Fixlmillner (1721–1791) – Benedictine priest and one of the first astronomers to compute the orbit of Uranus
- Paolo Frisi (1728–1784) – Priest, mathematician, and astronomer who did significant work in hydraulics
- José Gabriel Funes (1963– ) – Jesuit astronomer and current director of the Vatican Observatory
- Joseph Galien (1699 – c. 1762) – Dominican professor who wrote on aeronautics, hailstorms, and airships
- Jean Gallois (1632–1707) – French scholar, abbot, and member of Academie des sciences
- Pierre Gassendi (1592–1655) – French priest, astronomer, and mathematician who published the first data on the transit of Mercury; best known intellectual project attempted to reconcile Epicurean atomism with Christianity
- Agostino Gemelli (1878–1959) – Franciscan physician and psychologist; founded Catholic University of the Sacred Heart in Milan
- Johannes von Gmunden (c. 1380–1442) – Canon, mathematician, and astronomer who compiled astronomical tables; Asteroid 15955 Johannesgmunden named in his honor
- Carlos de Sigüenza y Góngora (1645–1700) – Priest, polymath, mathematician, astronomer, and cartographer; drew the first map of all of New Spain
- Andrew Gordon (Benedictine) (1712–1751) – Benedictine monk, physicist, and inventor who made the first electric motor
- Christoph Grienberger (1561–1636) – Jesuit astronomer after whom the crater Gruemberger on the Moon is named; verified Galileo's discovery of Jupiter's moons.
- Francesco Maria Grimaldi (1618–1663) – Jesuit who discovered the diffraction of light (indeed coined the term "diffraction"), investigated the free fall of objects, and built and used instruments to measure geological features on the moon
- Robert Grosseteste (c. 1175 – 1253) – Bishop who was one of the most knowledgeable men of the Middle Ages; has been called "the first man ever to write down a complete set of steps for performing a scientific experiment."
- Paul Guldin (1577–1643) – Jesuit mathematician and astronomer who discovered the Guldinus theorem to determine the surface and the volume of a solid of revolution
- Bartolomeu de Gusmão (1685–1724) – Jesuit known for his early work on lighter-than-air airship design
- Johann Georg Hagen (1847–1930) – Jesuit director of the Georgetown and Vatican Observatories; The crater Hagen on the Moon is named after him
- Nicholas Halma (1755–1828) – French abbot, mathematician, and translator
- Jean-Baptiste du Hamel (1624–1706) – French priest, natural philosopher, and secretary of the Academie Royale des Sciences
- René Just Haüy (1743–1822) – Priest known as the father of crystallography
- Maximilian Hell (1720–1792) – Jesuit astronomer and director of the Vienna Observatory; the crater Hell on the Moon is named after him.
- Michał Heller (1936– ) – Priest, Templeton Prize winner, and prolific writer on numerous scientific topics
- Lorenz Hengler (1806–1858) – Priest often credited as the inventor of the horizontal pendulum
- Hermann of Reichenau (1013–1054) – Benedictine historian, music theorist, astronomer, and mathematician
- Pierre Marie Heude (1836–1902) – Jesuit missionary and zoologist who studied the natural history of Eastern Asia
- Franz von Paula Hladnik (1773–1844) – Priest and botanist who discovered several new kinds of plants, and certain genera have been named after him
- Giovanni Battista Hodierna (1597–1660) – Priest and astronomer who catalogued nebulous objects and developed an early microscope
- Victor-Alphonse Huard (1853–1929) – Priest, naturalist, educator, writer, and promoter of the natural sciences
- Maximus von Imhof (1758–1817) – German Augustinian physicist and director of the Munich Academy of Sciences
- Giovanni Inghirami (1779–1851) – Italian Piarist astronomer who has a valley on the moon named after him as well as a crater
- François Jacquier (1711–1788) – Franciscan mathematician and physicist; at his death he was connected with nearly all the great scientific and literary societies of Europe
- Stanley Jaki (1924–2009) – Benedictine priest and prolific writer who wrote on the relationship between science and theology
- Ányos Jedlik (1800–1895) – Benedictine engineer, physicist, and inventor; considered by Hungarians and Slovaks to be the unsung father of the dynamo and electric motor
- Georg Joseph Kamel (1661–1706) – Jesuit missionary and botanist who established the first pharmacy in the Philippines
- Karl Kehrle (1898-1996) - Benedictine Monk of Buckfast Abbey, England. Beekeeper. World authority on bee breeding, developer of the Buckfast bee.
- Otto Kippes (1905–1994) – Priest acknowledged for his work in asteroid orbit calculations; the main belt asteroid 1780 Kippes was named in his honour
- Athanasius Kircher (1602–1680) – Jesuit who has been called the father of Egyptology and "Master of a hundred arts"; wrote an encyclopedia of China; one of the first people to observe microbes through a microscope
- Wenceslas Pantaleon Kirwitzer (1588–1626) – Jesuit astronomer and missionary who published observations of comets
- Jan Krzysztof Kluk (1739–1796) – Priest, naturalist agronomist, and entomologist who wrote a multi-volume work on Polish animal life
- Marian Wolfgang Koller (1792–1866) – Benedictine professor who wrote on astronomy, physics, and meteorology
- Franz Xaver Kugler (1862–1929) – Jesuit chemist, mathematician, and Assyriologist who is most noted for his studies of cuneiform tablets and Babylonian astronomy
- Ramon Llull (ca. 1232 – ca. 1315) Majorcan writer and philosopher, logician and a Franciscan tertiary considered a pioneer of computation theory
- Nicolas Louis de Lacaille (1713-1762) - French deacon and astronomer noted for cataloguing stars, nebulous objects, and constellations
- Eugene Lafont (1837–1908) – Jesuit physicist, astronomer, and founder of the first Scientific Society in India
- Antoine de Laloubère (1600–1664) – Jesuit and first mathematician to study the properties of the helix
- Bernard Lamy (1640–1715) – Oratorian philosopher and mathematician who wrote on the parallelogram of forces
- Pierre André Latreille (1762–1833) – Priest and entomologist whose works describing insects assigned many of the insect taxa still in use today
- Georges Lemaître (1894–1966) – Priest and father of the Big Bang Theory
- Thomas Linacre (c. 1460–1524) – English priest, humanist, translator, and physician
- Francis Line (1595–1675) – Jesuit magnetic clock and sundial maker who disagreed with some of the findings of Newton and Boyle
- Juan Caramuel y Lobkowitz (1606–1682) – Cistercian who wrote on a variety of scientific subjects, including probability theory
- Jean Mabillon (1632–1707) – Benedictine monk and scholar, considered the founder of palaeography and diplomatics
- James B. Macelwane (1883–1956) – "The best-known Jesuit seismologist" and "one of the most honored practicioners of the science of all time"; wrote the first textbook on seismology in America.
- John MacEnery (1797-1841) - Archaeologist who investigated the Palaeolithic remains at Kents Cavern
- Paul McNally (1890–1955) – Jesuit astronomer and director of Georgetown Observatory; the crater McNally on the Moon is named after him.
- Manuel Magri (1851–1907) – Jesuit ethnographer, archaeologist and writer; one of Malta's pioneers in archaeology
- Emmanuel Maignan (1601–1676) – Minim physicist and professor of medicine who published works on gnomonics and perspective
- Charles Malapert (1581–1630) – Jesuit writer, astronomer, and proponent of Aristotelian cosmology; also known for observations of sunpots and of the lunar surface, and the crater Malapert on the Moon is named after him
- Nicolas Malebranche (1638–1715) – Oratorian philosopher who studied physics, optics, and the laws of motion and disseminated the ideas of Descartes and Leibniz
- Marcin of Urzędów (c. 1500–1573) – Priest, physician, pharmacist, and botanist
- Joseph Maréchal (1878–1944) – Jesuit philosopher and psychologist
- Marie-Victorin (1885–1944) – Christian Brother and botanist best known as the father of the Jardin botanique de Montréal
- Edme Mariotte (c. 1620–1684) – Priest and physicist who recognized Boyle's Law and wrote about the nature of color
- Francesco Maurolico (1494–1575) – Benedictine who made contributions to the fields of geometry, optics, conics, mechanics, music, and astronomy, and gave the first known proof by mathematical induction
- Christian Mayer (astronomer) (1719–1783) – Jesuit astronomer most noted for pioneering the study of binary stars
- James Robert McConnell (1915-1999) - Irish Theoretical Physicist, Pontifical Academician, Monsignor
- Gregor Mendel (1822–1884) – Augustinian monk and father of genetics
- Pietro Mengoli (1626–1686) – Priest and mathematician who first posed the famous Basel Problem
- Giuseppe Mercalli (1850–1914) – Priest, volcanologist, and director of the Vesuvius Observatory who is best remembered today for his Mercalli scale for measuring earthquakes which is still in use
- Marin Mersenne (1588–1648) – Minim philosopher, mathematician, and music theorist who is often referred to as the "father of acoustics"
- Paul of Middelburg (1446–1534) – Bishop of Fossombrone who wrote important works on the reform of the calendar
- Maciej Miechowita (1457–1523) – Canon who wrote the first accurate geographical and ethnographical description of Eastern Europe, as well as two medical treatises
- François-Napoléon-Marie Moigno (1804–1884) – Jesuit physicist and mathematician; was an expositor of science and translator rather than an original investigator
- Juan Ignacio Molina (1740–1829) – Jesuit naturalist, historian, botanist, ornithologist and geographer
- Louis Moréri (1643–1680) – 17th century priest and encyclopaedist
- Théodore Moret (1602–1667) – Jesuit mathematician and author of the first mathematical dissertations ever defended in Prague; the lunar crater Moretus is named after him.
- Landell de Moura (1861–1928) – Priest and inventor who was the first to accomplish the transmission of the human voice by a wireless machine
- Gabriel Mouton (1618–1694) – Abbot, mathematician, astronomer, and early proponent of the metric system
- Jozef Murgaš (1864–1929) – Priest who contributed to wireless telegraphy and help develop mobile communications and wireless transmission of information and human voice
- José Celestino Mutis (1732–1808) – Canon, botanist, and mathematician who led the Royal Botanical Expedition of the New World
- Jean François Niceron (1613–1646) – Minim mathematician who studied geometrical optics
- Nicholas of Cusa (1401–1464) – Cardinal, philosopher, jurist, mathematician, astronomer, and one of the great geniuses and polymaths of the 15th century
- Julius Nieuwland (1878–1936) – Holy Cross priest, known for his contributions to acetylene research and its use as the basis for one type of synthetic rubber, which eventually led to the invention of neoprene by DuPont
- Jean-Antoine Nollet (1700–1770) – Abbot and physicist who discovered the phenomenon of osmosis in natural membranes.
- Hugo Obermaier (1877–1946) – Priest, prehistorian, and anthropologist who is known for his work on the diffusion of mankind in Europe during the Ice Age, as well as his work with north Spanish cave art
- William of Ockham (c. 1288 – c. 1348) – Franciscan Scholastic who wrote significant works on logic, physics, and theology; known for Ockham's Razor
- Nicole Oresme (c. 1323–1382) – One of the most famous and influential philosophers of the later Middle Ages; economist, mathematician, physicist, astronomer, philosopher, theologian and Bishop of Lisieux, and competent translator; one of the most original thinkers of the 14th century
- Barnaba Oriani (1752–1832) – Barnabite geodesist, astronomer and scientist whose greatest achievement was his detailed research of the planet Uranus, and is also known for Oriani's theorem
- Luca Pacioli (c. 1446–1517) – Franciscan friar who published several works on mathematics and is often regarded as the Father of Accounting
- Ignace-Gaston Pardies (1636–1673) – Jesuit physicist known for his correspondence with Newton and Descartes
- Franciscus Patricius (1529–1597) – Priest, cosmic theorist, philosopher, and Renaissance scholar
- John Peckham (1230–1292) – Archbishop of Canterbury and early practitioner of experimental science
- Nicolas Claude Fabri de Peiresc (1580–1637) – Abbot and astromer who discovered the Orion Nebula; lunar crater Peirescius named in his honor
- Stephen Joseph Perry (1833–1889) – Jesuit astronomer and Fellow of the Royal Society; made frequent observations of Jupiter's satellites, of stellar occultations, of comets, of meteorites, of sun spots, and faculae
- Giambattista Pianciani (1784–1862) – Jesuit mathematician and physicist
- Giuseppe Piazzi (1746–1826) – Theatine mathematician and astronomer who discovered Ceres, today known as the largest member of the asteroid belt; also did important work cataloguing stars
- Jean Picard (1620–1682) – Priest and first person to measure the size of the Earth to a reasonable degree of accuracy; also developed what became the standard method for measuring the right ascension of a celestial object; The PICARD mission, an orbiting solar observatory, is named in his honor
- Edward Pigot (1858–1929) – Jesuit seismologist and astronomer
- Alexandre Guy Pingré (1711–1796) – French priest astronomer and naval geographer; the crater Pingré on the Moon is named after him, as is the asteroid 12719 Pingré
- Andrew Pinsent (1966- ) – Priest whose current research includes the application of insights from autism and social cognition to 'second-person' accounts of moral perception and character formation. His previous scientific research contributed to the DELPHI experiment at CERN
- Jean Baptiste François Pitra (1812–1889) – Bendedictine cardinal, archaeologist and theologian who noteworthy for his great archaeological discoveries
- Charles Plumier (1646–1704) – Minim friar who is considered one of the most important botanical explorers of his time
- Marcin Odlanicki Poczobutt (1728–1810) – Jesuit astronomer and mathematician; granted the title of the King's Astronomer; the crater Poczobutt on the Moon is named after him.
- Léon Abel Provancher (1820–1892) – Priest and naturalist devoted to the study and description of the fauna and flora of Canada; his pioneer work won for him the appellation of the "Father of Natural History in Canada"
- Louis Receveur (1757–1788) – Franciscan naturalist and astronomer; described as being as close as one could get to being an ecologist in the 18th century
- Franz Reinzer (1661–1708) – Jesuit who wrote an in-depth meteorological, astrological, and political compendium covering topics such as comets, meteors, lightning, winds, fossils, metals, bodies of water, and subterranean treasures and secrets of the earth
- Louis Rendu (1789–1859) – Bishop who wrote an important book on the mechanisms of glacial motion; the Rendu Glacier, Alaska, U.S. and Mount Rendu, Antarctica are named for him
- Vincenzo Riccati (1707–1775) – Italian Jesuit mathematician and physicist
- Matteo Ricci (1552–1610) – One of the founding fathers of the Jesuit China Mission and co-author of the first European-Chinese dictionary
- Giovanni Battista Riccioli (1598–1671) – Jesuit astronomer who authored Almagestum novum, an influential encyclopedia of astronomy; The first person to measure the rate of acceleration of a freely falling body; created a selenograph with Father Grimaldi that now adorns the entrance at the National Air and Space Museum in Washington D.C.
- Richard of Wallingford (1292-1336) - Abbot, renowned clockmaker, and one of the initiators of western trigonometry
- Johannes Ruysch (c. 1460–1533) – Priest, explorer, cartographer, and astronomer who created the second oldest known printed representation of the New World
- Giovanni Girolamo Saccheri (1667–1733) – Jesuit mathematician and geometer
- Johannes de Sacrobosco (c. 1195 – c. 1256) – Irish monk and astronomer who wrote the authoritative medieval astronomy text Tractatus de Sphaera; his Algorismus was the first text to introduce Hindu-Arabic numerals and procedures into the European university curriculum; the lunar crater Sacrobosco is named after him
- Gregoire de Saint-Vincent (1584–1667) – Jesuit mathematician who made important contributions to the study of the hyperbola
- Alphonse Antonio de Sarasa (1618–1667) – Jesuit mathematician who contributed to the understanding of logarithms
- Christoph Scheiner (c. 1573–1650) – Jesuit physicist, astronomer, and inventor of the pantograph; wrote on a wide range of scientific subjects
- Wilhelm Schmidt (linguist) (1868–1954) – Austrian priest, linguist, anthropologist, and ethnologist.
- George Schoener (1864–1941) – Priest who became known in the United States as the "Padre of the Roses" for his experiments in rose breeding
- Gaspar Schott (1608–1666) – Jesuit physicist, astronomer, and natural philosopher who is most widely known for his works on hydraulic and mechanical instruments
- Franz Paula von Schrank (1747–1835) – Priest, botanist, entomologist, and prolific writer
- Berthold Schwarz (c. 14th century) – Franciscan friar and reputed inventor of gunpowder and firearms
- Anton Maria Schyrleus of Rheita (1604–1660) – Capuchin astronomer and optrician who built Kepler's telescope
- George Mary Searle (1839–1918) – Paulist astronomer and professor who discovered six galaxies
- Angelo Secchi (1818–1878) – Jesuit pioneer in astronomical spectroscopy, and one of the first scientists to state authoritatively that the sun is a star
- Alessandro Serpieri (1823–1885) – Priest, astronomer, and seismologist who studied shooting stars, and was the first to introduce the concept of the seismic radiant
- Gerolamo Sersale (1584–1654) – Jesuit astronomer and selenographer; his map of the moon can be seen in the Naval Observatory of San Fernando; the lunar crater Sirsalis is named after him
- Benedict Sestini (1816–1890) – Jesuit astronomer, mathematician and architect; studied sunspots and eclipses; wrote textbooks on a variety of mathematical subjects
- René François Walter de Sluse (1622–1685) – Canon and mathematician with a family of curves named after him
- Lazzaro Spallanzani (1729–1799) – Priest, biologist, and physiologist who made important contributions to the experimental study of bodily functions, animal reproduction, and essentially discovered echolocation; his research of biogenesis paved the way for the investigations of Louis Pasteur
- Valentin Stansel (1621–1705) – Jesuit astronomer who made important observations of comets
- Johan Stein (1871–1951) – Jesuit astronomer and director of the Vatican Observatory, which he modernized and relocated to Castel Gandolfo; the crater Stein on the far side of the Moon is named after him
- Nicolas Steno (1638–1686) – Bishop beatified by Pope John Paul II who is often called the father of geology and stratigraphy, and is known for Steno's principles
- Pope Sylvester II (c. 946–1003) – Prolific scholar who endorsed and promoted Arabic knowledge of arithmetic, mathematics, and astronomy in Europe, reintroducing the abacus and armillary sphere which had been lost to Europe since the end of the Greco-Roman era
- Alexius Sylvius Polonus (1593 – c. 1653) – Jesuit astronomer who studied sunspots and published a work on calendariography
- Ignacije Szentmartony (1718–1793) – Jesuit cartographer, mathematician, and astronomer who became a member of the expedition that worked on the rearrangement of the frontiers among colonies in South America
- André Tacquet (1612–1660) – Jesuit mathematician whose work laid the groundwork for the eventual discovery of calculus
- Pierre Teilhard de Chardin (1881–1955) – Jesuit paleontologist and geologist who took part in the discovery of Peking Man
- Francesco Lana de Terzi (c. 1631–1687) – Jesuit referred to as the Father of Aviation for his pioneering efforts; he also developed a blind writing alphabet prior to Braille.
- Theodoric of Freiberg (c. 1250 – c. 1310) – Dominican theologian and physicist who gave the first correct geometrical analysis of the rainbow
- Joseph Tiefenthaler (1710–1785) – Jesuit who was one of the earliest European geographers to write about India
- Giuseppe Toaldo (1719–1797) – Priest and physicist who studied atmospheric electricity and did important work with lightning rods; the asteroid 23685 Toaldo is named for him.
- José Torrubia (c. 1700–1768) – Franciscan linguist, scientist, collector of fossils and books, and writer on historical, political and religious subjects
- Franz de Paula Triesnecker (1745–1817) – Jesuit astronomer and director of the Vienna Observatory; published a number of treatises on astronomy and geography; the crater Triesnecker on the Moon is named after him.
- Luca Valerio (1552–1618) – Jesuit mathematician who developed ways to find volumes and centers of gravity of solid bodies
- Pierre Varignon (1654–1722) – Priest and mathematician whose principle contributions were to statics and mechanics; created a mechanical explanation of gravitation
- Jacques de Vaucanson (1709–1782) – French Minim friar inventor and artist who was responsible for the creation of impressive and innovative automata and machines such as the first completely automated loom.
- Giovanni Battista Venturi (1746–1822) – Priest who discovered the Venturi effect
- Fausto Veranzio (c. 1551–1617) – Bishop, polymath, inventor, and lexicographer
- Ferdinand Verbiest (1623–1688) – Jesuit astronomer and mathematician; designed what some claim to be the first ever self-propelled vehicle – many claim this as the world's first automobile
- Francesco de Vico (1805–1848) – Jesuit astronomer who discovered or co-discovered a number of comets; also made observations of Saturn and the gaps in its rings; the lunar crater De Vico and the asteroid 20103 de Vico are named after him
- Vincent of Beauvais (c.1190–c.1264) – Dominican who wrote the most influential encyclopedia of the Middle Ages
- Benito Viñes (1837–1893) – Jesuit meteorologist who made the first weather model to predict the trajectory of a hurricane.   
- János Vitéz (archbishop) (c.1405–1472) – Archbishop, astronomer, and mathematician
- Martin Waldseemüller (c. 1470–1520) – German priest and cartographer who, along with Matthias Ringmann, is credited with the first recorded usage of the word America
- Godefroy Wendelin (1580–1667) – Priest and astronomer who recognized that Kepler's third law applied to the satellites of Jupiter; the lunar crate Vendelinus is named in his honor
- Johannes Werner (1468–1522) – Priest, mathematician, astronomer, and geographer
- Witelo (c. 1230 – after 1280, before 1314) – Friar, physicist, natural philosopher, and mathematician; lunar crater Vitello named in his honor; his Perspectiva powerfully influenced later scientists, in particular Johannes Kepler
- Julian Tenison Woods (1832–1889) – Passionist geologist and mineralogist
- Theodor Wulf (1868–1946) – Jesuit physicist who was one of the first experimenters to detect excess atmospheric radiation
- Franz Xaver von Wulfen (1728-1805) - Jesuit botanist, mineralogist, and alpinist
- John Zahm (1851–1921) – Holy Cross priest and South American explorer
- Giuseppe Zamboni (1776–1846) – Priest and physicist who invented the Zamboni pile, an early electric battery similar to the Voltaic pile
- Francesco Zantedeschi (1797–1873) – Priest who was among the first to recognize the marked absorption by the atmosphere of red, yellow, and green light; published papers on the production of electric currents in closed circuits by the approach and withdrawal of a magnet, thereby anticipating Michael Faraday's classical experiments of 1831
- Niccolò Zucchi (1586–1670) – claimed to have tried to build a reflecting telescope in 1616 but abandoned the idea (maybe due to the poor quality of the mirror). May have been the first to see the belts on the planet Jupiter (1630).
- Giovanni Battista Zupi (c. 1590–1650) – Jesuit astronomer, mathematician, and first person to discover that the planet Mercury had orbital phases; the crater Zupus on the Moon is named after him.
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