Carlo Ancelotti is now the head coach of Real Madrid, his second stint at the club.
The 61-year-old Italian, who managed Real Madrid for two years between 2013 and 2015, has left Everton after 18 months in charge at Goodison Park, where he led the Toffees to a 10th place finish.
Ancelotti has signed a three-year deal at Real and said the move represented "an unexpected opportunity".
He succeeds Zinedine Zidane at Real and the move leaves Everton searching for a sixth permanent manager in five years.
In a statement released Tuesday, June 1, Ancelotti said: "I have complete respect for everyone associated with Everton and hope they can achieve the exciting opportunities they have in front of them.
"While I have enjoyed being at Everton I have been presented with an unexpected opportunity which I believe is the right move for me and my family at this time."
Real Madrid will present Ancelotti to the media on Wednesday, while Everton said they "will begin the process of appointing a new manager immediately".
Ancelotti has won 15 major trophies during his career and is one of only three managers to win three European Cups - along with Liverpool legend Bob Paisley and former Real boss Zidane.
The Italian has domestic titles with AC Milan in his homeland, Chelsea in England, Paris St-Germain in France and also in Germany with Bayern Munich.