Martin Hugh Michael O'Neill, (born 1 March 1952) is a Northern Irish professional football manager and former player who played as a midfielder.
He was most recently manager of Championship club Nottingham Forest.
Starting his career in Northern Ireland, O'Neill moved to England where he spent most of his playing career with Nottingham Forest, with whom he won 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.
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 three Scottish Premier League titles and 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.