The Italian left two hours after defeat at Everton.
PA Sport says Ancelotti was given his marching orders by chief executive Ron Gourlay at Goodison Park after completing his post-match media duties.
"The owner and board would like to thank Carlo for his contribution and achievements since taking over as manager in July 2009, which included winning the Double for the first time in the club's history.
"However, this season's performances have fallen short of expectations and the club feels the time is right to make this change ahead of next season's preparations.
"Carlo will always be welcome at Stamford Bridge, where he will be given the reception and respect his position in our history deserves.
"Chelsea's long-term football objectives and ambitions remain unchanged and we will now be concentrating all our efforts on identifying a new manager.
"There will be no further comment until that appointment is made."