Octave Gengou (1875 – 1957) was a Belgian bacteriologist. He researched with Jules Bordet the Bordetella pertussis bacteria.
Gengou worked at the Belgium Pasteur Institute in Brussels. With Jules Bordet in 1906 he isolated Bordetella pertussis in pure culture and declared is as the cause of whooping cough. 1912 he developed the first whooping cough-vaccine. He also worked on various important fundamental research on a now common test for diseases (e.G. the Wassermann-Test of August von Wassermann)