Albert Ludwig Sigesmund Neisser (22 January 1855, Schweidnitz – 30 July 1916, Breslau) was a German physician who discovered the causative agent (pathogen) of gonorrhea, a strain of bacteria that was named in his honour (Neisseria gonorrhoeae).

He found work, however as an assistant of the dermatologist Oskar Simon (1845–1892), concentrating on sexually transmitted diseases and leprosy.

Neisser successfully stained the bacteria and announced his findings in 1880, claiming to have discovered the pathogenesis of leprosy.

[1] Though the majority of his contemporary academic physicians supported him, Neisser was investigated by the Prussian public prosecutor and ultimately fined for failing to obtain consent.

He later cooperated with August Paul von Wassermann (1866–1925) to develop the famous diagnostic test for detecting Treponema pallidum infections, and also in the testing of the first chemotherapeutic agent for syphilis, Salvarsan, which was discovered by his former school fellow Paul Ehrlich in 1910.

The Albert Neisser Lectureship has been awarded since 2005 by the Department of Dermatology at the University of Wrocław to dermatologists who have made significant clinical and research contributions to the field.