The Manchester City right-back has joined AC Milan on loan until the end of the season, with an option to buy at the end of the season for a fee of €5m, keeping him at the club until 2027.
The England international surprised Pep Guardiola and Manchester City in January when he asked to leave the club before the transfer window closed.
Kyle Walker, 34, joined Manchester City from Tottenham for €52.7 million in 2017, meaning he has spent eight years at the club, making 319 appearances, winning the Champions League and six Premier League titles with the club and various other honours.