Notable : Famous : Founder/ originator

Cornelis Adriaan Lobry van Troostenburg de Bruyn (1 January 1857 – 23 July 1904) was a chemist from the Netherlands.

Antonino Lo Surdo (4 February 1880 in Syracuse – 7 June 1949 in Rome) was an Italian physicist. He was appointed as professor of physics at the Istituto di Fisica in Rome in 1919; upon the death of Orso Mario Corbino in 1937, he became the director. Lo Surdo studied terrestrial physics, including seismology and geophysics; the 1908 Messina earthquake caused the death of his parents and other close relatives, except his brother. He contributed to the foundation of the Istituto Nazionale di Geofisica under the auspices of the Consiglio Nazionale delle Ricerche, when its president was Guglielmo Marconi.
His name is remembered for the discovery (made independently by Johannes Stark) in 1913 of the effect on an electric field on the emission spectrum of a gas. This physical phenomenon is called the Stark-Lo Surdo effect in Italy (and is generally known outside Italy simply as the Stark effect). The discovery of the effect was a remarkably important contribution to the development of the quantum theory. Lo Surdo's discovery of the effect led Antonio Garbasso to introduce quantum theory into the Italian universities.

Friedrich Hermann Leuchs (8 August 1879 – 2 May 1945) was a German chemist.

Friedrich Wilhelm Erich Leschke (23 October 1887, in Bergneustadt – 10 June 1933, in Berlin) was a German internist.
He studied medicine at the University of Bonn, receiving his doctorate in 1911 with the thesis Über die Wirkung des Pankreasextraktes auf pankreasdiabetische und auf normale Tiere ("On the effect of pancreatic extract on pancreatic-diabetic and normal animals"). He later worked at the Friedrich-Wilhelm-Stift in Bonn, at the Eppendorf Hospital in Hamburg and in the 2nd medical clinic at the Berlin Charité. In 1918 he obtained his habilitation at Berlin, where soon afterwards he became an associate professor.His name is associated with Leschke's syndrome, a condition characterized by a combination of asthenia, multiple brown pigment spots on the skin and hyperglycemia. He described the syndrome in a 1922 paper titled Über Pigmentierung bei Funktionsstörungen der Nebenniere und des sympathischen Nervensystems bei der Recklinghausenschen Krankheit.He was the author of numerous papers regarding cardiac, pulmonary and metabolic diseases. His book Die wichtigsten vergiftungen, Fortschritte in deren Erkennung und Behandlung was translated into English and published as Clinical toxicology; modern methods in the diagnosis and treatment of poisoning (1934).

Marcel Lermoyez (24 July 1858 – 1 February 1929) was a French otolaryngologist and surgeon who was a native of Cambrai.

Clément Georges Lemoine (16 January 1841 in Tonnerre – 13 November 1922 in Paris) was a French chemist and hydrologist. He was the father of geologist Paul Lemoine (1878–1940).
He studied at the École Polytechnique and the École des ponts et chaussées, obtaining a doctorate in physical sciences in 1865. For many years he was associated with the École Polytechnique in Paris, where he ultimately served as a professor of chemistry from 1898 to 1911.In 1866 he began work as an engineer in charge of hydrometric services in the Seine Basin. In 1881 he was appointed chief engineer of bridges and roads, and in 1901, was named inspector general of bridges and roads. He is credited with organizing a flood warning service throughout France.As a chemist he discovered phosphorus sesquisulfide, a compound that will later be used in the manufacture of matches. He continued research on the allotropic transformation of phosphorus, and was also the author of works on chemical equilibria.In 1899 he became a member of the Académie des sciences (chemistry section), of which in 1921, he was named its president.

André-Alfred Lemierre (July 30, 1875 in Paris – 1956) was a French bacteriologist.He studied in Paris where he became an externe in 1896, interne in 1900. He obtained his doctorate in 1904, became Médecin de Hôpitaux in 1912 and later worked in the Hôpital Bichat. He was habilitated in 1913 and in 1926 was promoted to professor of bacteriology. His works concern investigations on septicaemia, typhus, bilious and urine tract infections, kidney diseases, etc. He described Lemierre's syndrome in 1936 while working as a bacteriologist in the Claude Bernard Hospital in Paris.

Otto Michael Ludwig Leichtenstern (14 October 1845 – 23 February 1900) was a German internist born in Ingolstadt.
In 1869 he received his doctorate from the University of Munich, later working as an assistant of clinical medicine in Munich under Karl von Pfeufer (1806–1869) and Joseph von Lindwurm (1824–1874). After the death of Felix von Niemeyer (1820–1871), he served as interim head of the medical clinic in Tübingen prior to the appointment of Carl von Liebermeister (1833–1901) as Niemeyer's permanent replacement. Leichtenstern remained at the Tübingen clinic for several years, afterwards serving as head physician of internal medicine at the city hospital in Cologne (1879–1900).
Leichtenstern is remembered for publishing articles on almost every facet of medicine. In the field of helminthology, he made contributions in his investigations of hookworm (Ancylostoma duodenale).In 1898 he suspected that the compound 2-naphthylamine (2-NA) was involved in human bladder tumorigenesis. With Adolph Strümpell (1853–1925), the eponymous "Strümpell-Leichtenstern encephalitis" is named, a disease also known as acute hemorrhagic encephalitis.

Félix Legueu (12 August 1863 – 2 October 1939) was a French urologist and gynecologist born in Angers.