The Northern Irishman stood down from his post this morning after four years with the Scottish champions.
In a statement via the club's official website, Lennon said: "I have supported Celtic all my life and the club will always be part of me. It was an absolute honour to play for this great club, to captain the team and of course to become Celtic manager - a position which I cherished dearly. However, I feel the time is now right to move on to a new challenge.
"Of course, I am very pleased that I will be leaving Celtic as Scottish champions and with the club in such good health. I wish the club nothing but good fortune going forward.
"Serving the club was always a privilege. I have always given my best and aimed to do all I can to ensure success for Celtic, as a supporter it was all I wanted. I will now assist the club in appointing my successor. As ever, we will need our fans' support and I am sure they will give the club and the new manager the same great backing which they gave to myself."
Lennon, who has been linked to Norwich City and West Bromwich Albion, guided Celtic to three league titles and two Scottish Cups.