Manchester City have signed John Stones from Everton for £47.5m, making him the world's second most expensive defender.
The 22-year-old England international has signed a six-year deal and is City boss Pep Guardiola's eighth signing.
Stones was earlier named in City's official Champions League squad, published on the Uefa website before the transfer was confirmed.
"It's an ambitious club with a great manager so I can't wait to get stuck in," said the former Barnsley player.
"I know it will be tough getting a place in this team, but I'm determined to become the best player I can be and help us to success."
In a short statement, Everton confirmed they had received a "record fee" for Stones, who made 95 appearances in three seasons, scoring once.
Championship side Barnsley, the Yorkshireman's first club, will get between £7m and £9m from a sell-on clause.
Everton, meanwhile, have had a £12m bid accepted for Swansea centre-half Ashley Williams, 31.
Brazil international David Luiz is the most expensive defender in history, joining French champions Paris St-Germain from Chelsea for £50m in 2014.
Last year, City made Raheem Sterling the most expensive English player ever when he joined the club for £49m from Liverpool.
City have already signed Ilkay Gundogan, Nolito, Leroy Sane, Gabriel Jesus, Marlos Moreno, Aaron Mooy and Oleksandr Zinchenko this summer.
Their first Premier League fixture is at home to Sunderland on Saturday.
Why have City bought Stones?
Their statement described Stones as "one of the world's most promising centre-backs" with a reputation as a "ball-playing, 21st-century defender".
City also claim he is at his best when "neutralising opposition attacks" and "launching the first key pass out of the defensive third".
Guardiola said: "We want to help John show his quality with us and improve on what he has already achieved. I like the way he plays the game and I'm looking forward to welcoming him into the squad."
City's director of football, Txiki Begiristain, said the club had "worked hard" to sign him and regard him as "one of the best central defenders in Europe".
The rise of Stones
Stones joined Barnsley's academy at the age of seven and stayed at the club for 12 years.
He made his Tykes debut at the age of 17 and made 24 league appearances before moving to Everton in January 2013 for a fee thought to be about £3m.
Stones has made 95 appearances for the Toffees in three seasons, scoring once, and has 10 international caps.
He was part of the England squad at Euro 2016 but did not feature as they were knocked out in the last 16 by Iceland.
Criticised by some Everton supporters and former players such as Sol Campbell for making mistakes, Stones made the joint most errors directly leading to goals in the last season's Premier League season - three.
Only former Everton team-mate Phil Jagielka, Southampton's Maya Yoshida and West Ham's Aaron Cresswell made as many.
|How Stones compared to some of Europe's top defenders last season|
|Player||Minutes played||Fouls conceded||Passing accuracy (%)||Duels success (%)|
Top five other English signings
- 2015 - Raheem Sterling £49m (Liverpool to Manchester City)
- 2011 - Andy Carroll £35m (Newcastle to Liverpool)
- 2002 - Rio Ferdinand £30m (Leeds to Manchester United)
- 2014 - Luke Shaw £27m (Southampton to Manchester United)
- 2004 - Wayne Rooney £27m (Everton to Manchester United)
World's most expensive defenders
- 2014 - David Luiz £50m (Chelsea to Paris St-Germain)
- 2016 - John Stones £47.5m (Everton to Manchester City)
- 2012 - Thiago Silva £36m (AC Milan to Paris St-Germain)
- 2014 - Eliaquim Mangala £32m (Porto to Manchester City)
- 2015 - Nicolas Otamendi £32m (Valencia to Manchester City)