is a Northern Irish professional football manager and former player who played as a midfielder. After a brief early career in the Irish League, O'Neill moved to England where he spent most of his playing career with Nottingham Forest. He won the First Division title in 1977–78 and the European Cup twice, in 1979 and 1980. He was capped 64 times for the Northern Ireland national football team, also captaining the side at the 1982 World Cup.

At club level, O'Neill has managed Grantham Town, Wycombe Wanderers, Norwich City, Leicester City, Celtic, Aston Villa and Sunderland. He guided Leicester City to the Football League Cup final three times, winning twice. As Celtic manager between 2000 and 2005, he led that club to seven trophies including three Scottish Premier League titles, and also reached the 2003 UEFA Cup Final. After joining Aston Villa he achieved three consecutive sixth-place finishes in the English Premier League and guided them to the 2010 Football League Cup Final.

He became Republic of Ireland manager in 2013 and led them to qualification for the 2016 UEFA European Championship for the third time in the nation's history, beating the reigning world champions, Germany, in the process. He left the role with assistant Roy Keane by \"mutual agreement\" in November 2018. He was appointed as Nottingham Forest manager in January 2019 but parted ways with the club in June of the same year.