The Northern Irishman took over from Tony Mowbray in March 2010, initially on a caretaker basis, before being given the job on a full-time basis at the start of the 2010-11 campaign.
Lennon spent seven years as a player at the club and further endeared himself to the Celtic Park faithful by delivering consecutive Scottish Premiership titles in his last three seasons at the helm.
He also guided the club to two Scottish Cups, in 2011 and 2013, but it was announced on Thursday that he would not continue as manager in 2014-15.
Lennon has been heavily linked with the vacant position at Norwich City and reportedly held concerns over Celtic's playing budget for next season, with the club looking to make progress in the UEFA Champions League.
"I have parted company with Celtic," said Lennon in a brief statement, according to BBC Sport.
"The club are in a very strong position and I wish the fans and the club all the very best for the future.
"I can't thank (chief executive) Peter Lawwell and the board enough for their backing and support during my time as manager."
