Lennon had began the campaign hoping to take the club to an historic 10th straight league title but the Glasgow giants have endured a dreadful campaign by their own high standards and, following Sunday’s 1-0 defeat at Ross County trail Premiership leaders Rangers by 18 points.
They were also knocked out of the League Cup by Ross County in the second round back in November, and finished rock-bottom of their Europa League group, having slipped into the secondary European competition after falling to Hungarian side Ferencvaros in Champions League qualifying.
Lennon’s assistant, John Kennedy, has been placed in interim charge.
Lennon said: “We have experienced a difficult season due to so many factors and, of course, it is very frustrating and disappointing that we have not been able to hit the same heights as we did previously.
“I have worked as hard as ever to try and turn things around, but unfortunately we have not managed to get the kind of run going that we have needed.
“I have always given my best to the Club and have been proud to deliver silverware to the Celtic supporters. The Club will always be part of me. I will always be a Celtic supporter myself and I will always want the best for Celtic.
“I would like to thank so many people at the Club who have given me so much and I would also like to thank my family for their love and support. I wish the Celtic supporters, players, staff and directors nothing but success for the future.”