L
- Henri Laborit (1914–1995), French surgeon and physiologist
- Bernard Germain Étienne de la Ville, Comte de Lacépède (1756–1825), French naturalist
- David Lack (1910–1973), British ornithologist
- Frédéric de Lafresnaye (1783–1861), French ornithologist
- Jean-Baptiste Lamarck (1744–1829), French evolutionist, coined many terms like biology and fossils
- Aylmer Bourke Lambert (1761–1842), British botanist
- Charles Lamberton (fl. 1912–1956), French paleontologist
- Hugh Lamprey (1928–1996), British ecologist
- Kai Larsen (born 1926), Danish botanist
- Charles Francis Laseron (1887–1959), American-born Australian naturalist and malacologist
- John Latham (1740–1837), English naturalist
- Pierre André Latreille (1762–1833), French entomologist
- Charles Louis Alphonse Laveran (1845–1922), French physician, winner of the 1907 Nobel Prize in Physiology or Medicine for his discovery that the cause of malaria is a protozoon
- George Newbold Lawrence (1806–1855), American ornithologist
- William Elford Leach (1790–1836), English zoologist and marine biologist
- Colin Leakey (born 1933), British tropical botanist and specialist in bean science
- Joseph LeConte (1823–1901), physiologist
- Tim Lee (born 1977), comedian
- Antoni van Leeuwenhoek (1632–1723), Dutch biologist, developer of the microscope
- François Leguat (c. 1637 – 1735), French naturalist
- Joseph Leidy (1823–1891), American paleontologist
- Johann Philipp Achilles Leisler (1771–1813), Dutch naturalist
- Juan Lembeye (1816–1889), Spanish naturalist
- Leonardo Da Vinci (1452–1519), known as an artist but also an anatomist. Dissected hundreds of specimens and drew exact copies of them
- Jean Baptiste Leschenault de la Tour (1773–1826), French botanist
- Rene Primevere Lesson (1794–1849), French naturalist
- Charles Alexandre Lesueur (1778–1846), French naturalist
- François Le Vaillant (1753–1824), French ornithologist
- Richard Lewontin (born 1929), biologist
- Wen-Hsiung Li, molecular evolutionary biologist
- Emmanuel Liais (1826–1900), French botanist
- Martin Lichtenstein (1780–1867), German zoologist
- John Lightfoot (1735–1788), English conchologist and botanist
- David R. Lindberg, American malacologist and biologist
- Aristid Lindenmayer (1925–1989), Hungarian biologist
- John Lindley (1799–1865), English botanist
- Heinrich Friedrich Link (1767–1850), German botanist (abbr. in botany: Link)
- Carolus Linnaeus (1707–1778), Swedish botanist; father of the binomial nomenclature system (abbr L. or Linn.)
- Jacques Loeb (1859–1924), German-American biologist
- Friedrich Loeffler (1852–1915), German biologist
- Konrad Lorenz (1903–1989), Austrian founder of ethology
- Harri Lorenzi (born 1949), Brazilian botanist
- John Claudius Loudon (1783–1843), English botanist
- James Lovelock (born 1919), English chemist and father of the Gaia hypothesis
- Percy Lowe (1870–1948), English ornithologist
- Peter Wilhelm Lund (1801–1880), Danish zoologist and paleontologist
- Salvador Luria (1912–1991), microbiologist, Nobel prize winner
- Adolfo Lutz (1855–1940), Brazilian infectologist, pathologist and public health researcher
- André Lwoff (1902–1994), French microbiologist, winner of the 1965 Nobel Prize in Physiology or Medicine
- Richard Lydekker (1849–1915), English naturalist
- Trofim Lysenko (1898–1976), Soviet biologist and agronomist. His denouncement of genetics became known as Lysenkoism.
Read more about this topic: List Of Biologists