Páidí O'Brien (born 13 February 1984 in Cork, Ireland) is an Irish professional cyclist. He won the National Under-23 Road Race Championships twice, and in the senior National Road Race Championships, O'Brien has twice came second and third three times.

O'Brien was a member of the team time trial squad that won the opening stage of Vuelta a Extremadura in April 2008. As first of the team across the line, he wore the leader's jersey for the second stage. He lost nine seconds and the jersey went to team-mate Benny De Schrooder.