Williams had managed Colchester since July 2006
Colchester United have announced that their manager Geraint Williams has parted company with the club.
The U's are currently second from bottom of League One, following their 3-0 home defeat by MK Dons on Saturday.
Chairman Robbie Cowling paid tribute to Williams: "I am grateful to him for leaving the club in a much better state than when he joined it."
Colchester have named assistant boss Kit Symons as caretaker manager following Williams' departure.
Colwing added: "In my opinion, Geraint was badly let down on Saturday by some of his players who failed to play for him, some of our supporters who failed to support him and by myself for failing to publicly back him before it was too late.
"I have been privileged to meet and work with some great people and Geraint is up there with the best.
"Despite our poor start, I have every confidence that Geraint has built a good squad which most certainly will gel."
Williams spent a decade at Colchester having joined in 1998 as a player, before becoming a coach, then manager in 2006 following the departure of Phil Parkinson.
He guided the club to the best-ever finish in 2006/07, when they ended up 10th in the Championship, before being relegated the following season.