The England global defender has penned a five-year deal at Goodison Park.
The former Burnley and Manchester United defender told the official club website: 'I'm absolutely delighted to be at Everton, a fantastic football club with passionate fans a great tradition. "I have been fortunate enough that in the clubs I have played in the past, the manager has played in my position as well and I feel like he was a very classy centre-half so he can still teach me things".
The 24-year-old Keane was contracted for five years to June 2022. I feel like this is a great place to come and continue my development as a player.
Keane was one of the outstanding defenders in the Premier League this past season and his performances have led to him being included in the England setup.
"I suppose - similar to Gerard Pique - he needed to go somewhere else to get a run of games and prove himself again".
Everton boss Ronald Koeman has prioritised the signing of the 24-year-old this summer as he looks to strengthen his defensive options.
Ronald Koeman believes the £30 million signing of England defender Michael Keane offers another clear statement of Everton's ambition as the manager took his summer spending to nearly £100 million. At that point, all the coaching staff had seen his potential and thought he had a chance to play in the first team.
"We knew there would be competition from other clubs, but Michael believes in the ambition of Everton and what we want to do and this is the flawless moment for him to come".
As a reward for his fine form, Keane was called up to the senior England squad in October for two FIFA World Cup qualifying matches, and he earned his first cap in a friendly against Germany on March 22.