The ex-Hoops manager and player is having a disastrous time in his managerial career at present.
Lennon, who has been embroiled in controversy since taking the job in May, has been let go.
His team are in 12th place in the Romanian domestic league, which is a lot lower than usual for them.
After five draws and a defeat, Rapid have decided to pull the plug and hire Marius Sumudica.
A club statement read: “Rapid parted company with Northern Irish coach Neil Lennon today, after only six stages of the current Romanian SuperLiga season.
“Arriving this summer, Neil Lennon did not manage to get any victory on the bench of Rapid, finishing five times in a draw and losing one match.
“Along with Neil, other members of his staff will also leave, Iain Brunskill, Andrew Liddell and Kyirakos Televantos.
“We thank Neil for all his dedication and energy on the Rapid bench, especially since he has been through difficult times lately, and we wish him much success in the future.
“Our club is pleased to announce the return of Marius Sumudica, a pure-blood Rapid player, who is our new head coach.”