Piergiorgio Odifreddi (1950- )
Doris Olin
Alberto Oliverio (= Αλμπέρτο Ολιβέριο)
Onora O' Neill (1941- )
Michel Onfray (= Μισέλ Ονφρέ, 1959- ) (A), (B)
Patrick Jake O' Rourke (= O' Rourke, 1947- )