The 53-year-old ex-Northern Ireland midfielder, who also had spells in charge at Bolton Wanderers and Omonia Nicosia, was appointed in May.
A run of five draws and a defeat has Rapid sitting 12th in the 16-team SuperLiga.
Backroom staff Iain Brunskill, Andrew Liddell and Kyirakos Televantos have also been relieved of their duties.
A club statement on Lennon’s departure read: “We thank him for all his dedication and energy on the Rapidu bench, especially since he has been through difficult times lately, and we wish him much success in the future!”
Lennon, who also captained Celtic, had been at home in Northern Ireland earlier this month following the death of his mother.
