Manchester City have completed the signing of Monaco full-back Benjamin Mendy from Monaco, both clubs confirmed on Monday.
Neither club disclosed the fee, but sources told ESPN FC at the weekend that the deal could be worth up to £52 million, which would be a record for a defender, eclipsing City's deal earlier this month for Kyle Walker, which could reach £50m.
City will reportedly pay an initial fee of £49.4m, taking their summer spending past the £200 million mark.
"I am absolutely delighted to be joining Manchester City," Mendy told City's official website. "They are one of Europe's leading clubs and in Pep Guardiola they have a manager committed to playing attacking football. I am sure that over the next few years we will be successful."
Txiki Begiristain, City's director of football, added: "Benjamin has all the qualities we are looking for in a full-back. For such a young player, he has a wealth of top-level experience.
"He is undoubtedly one of the world's best full-backs, our No. 1 target in this position. We are all delighted to have him here at Manchester City. I'm sure he will prove a fantastic addition to the squad."
The 23-year-old left-back was a top target for Guardiola, who wanted to bring three new full-backs to the Etihad this summer after allowing Pablo Zabaleta, Bacary Sagna and Gael Clichy to leave at the end of last season when their contracts expired.
Mendy's arrival fills an opening on the left side of defence for City, who this summer have also signed right-back Walker from Tottenham as well as Danilo from Real Madrid (£26.5m), goalkeeper Ederson (£34.7m) and midfielders Douglas Luiz (£10m) and Bernardo Silva (£43m).
Premier League champions Chelsea had also been linked to a move for Mendy, a France international.
He will join a unit which already includes John Stones, Nicolas Otemendi, and the now-unwanted Eliaquim Mangala.
"I think I am the right person for the group. I am easily adaptable," Mendy told City's website. "There are some players with whom I exchanged a few emails, [as] I knew them from some years ago.
"I can bring a lot of creativity in the game, I can offer different solutions, I like to take to play as full-back and provide assists for the strikers. I am very proud of joining Manchester City, this is what I wanted from the very beginning.
"As soon as the championship was over, I talked to my family and it was all clear in my head, I wanted to join Manchester City. I'm really happy about it."
His Monaco contract was set to run until the summer of 2021, but the former Marseille man spent just one season in the principality, playing 25 games and providing five assists in the club's Ligue 1 title-winning campaign last term.
He supplied a further four assists in the Champions League, where he helped Monaco to the semifinals before bowing out to runners-up Juventus.
Mendy, who began his career at Le Havre, was a youth international at Under-17, U18, U19 and U21 level for France.