Luiz Felipe Scolari has been sacked as Chelsea manager, the club announced on Monday afternoon.
A statement on the club's official website revealed the move had been made "to maintain a challenge for the trophies we are still competing for".
Brazilian Scolari was appointed last summer as the replacement for Avram Grant.
The statement on the club's official website added: "Felipe has brought many positives to the club since he joined, and we all feel a sense of sadness that our relationship has ended so soon.
"Unfortunately the results and performances of the team appeared to be deteriorating at a key time in the season.
"In order to maintain a challenge for the trophies we are still competing for, we felt the only option was to make the change now.
"The search for a new manager has already started, and we hope to have someone in place as soon as possible."
Scolari's final game in charge was a goalless draw at home to Hull on Saturday, a result which was met with boos at the final whistle.
Assistant coach Ray Wilkins has been placed in temporary charge.