Ronald Koeman was hired to manage Everton on Tuesday after quitting English Premier League rival Southampton.
Southampton said it has begun a search for Koeman's replacement. The 53-year-old former Barcelona player had only a year remaining on his contract at Southampton, which he led to seventh and sixth place in his two years in charge.
"Everton is a club with a great history and real ambition, and it is a proud feeling for me to be part of what we want to go and do," Koeman said after signing a three-year contract at Everton.
The northwest England club, which fired Roberto Martinez last month after finishing 11th, has greater financial power since the recent takeover by Iranian-British businessman Farhad Moshiri.
"We are really pleased to have secured the man who was our No. 1 target from the moment we set out to appoint a new manager," chairman Bill Kenwright said.
"Ronald has such a strong track record in the game, instantly commanding respect for what he achieved as a player, and for his qualities and accomplishments as a manager."
Koeman has coached across Europe, winning the Dutch league twice with Ajax and domestic cups with Benfica in Portugal and Valencia in Spain.
As a player, Koeman won the European Cup with PSV Eindhoven in 1988 and Barcelona in 1992. Koeman made 82 appearances for the Netherlands.