Dutchman Ronald Koeman was named as Everton's new manager on Tuesday after Premier League rivals Southampton reluctantly accepted his resignation.
Everton had targeted former Ajax Amsterdam coach Koeman since parting company with Roberto Martinez last month.
"We are really pleased to have secured the man who was our number one target from the moment we set out to appoint a new manager," chairman Bill Kenwright said on the Everton website.
"The hopes and aspirations that we all have as Evertonians are with him, as is our total support at board, shareholder and fan level."
Koeman, a European Cup winner as a player with Barcelona, joined Southampton from Feyenoord in 2014, guiding them to seventh place in his first season and sixth last term, earning a Europa League spot.
Everton finished a disappointing 11th last season but are set for significant investment after Iranian businessman Farhad Moshiri purchased a 49.9 percent stake in the Merseyside club.
"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, together with the chairman and Farhad Moshiri," Koeman, 53, told www.evertonfc.com.
"I am looking forward to meeting everyone at the club and to preparing for a big season in the Premier League."
Confirming Koeman's departure, Southampton said the hunt had already started for his replacement.
"The search has already begun for the right appointment who can take the club to the next level and build on our track record of recent success," a statement said.
"Our focus now is to build on our long-term plan, and work with a new management team who share both the club's and our supporters' values and ambitions."
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