Patric Denis O'Brien ONZM (born 19 July 1959), commonly known as Paddy O'Brien, is a New Zealand international rugby union referee, and former head of the International Rugby Board's Referee Board. He was born in Southland, New Zealand. He played his rugby as a full back and wing for Southland at Under 18 and B level, as well as Sevens, between 1976 and 1984.