The Bradford-born midfielder, 25, completed a medical on Friday and will fly to Australia over the weekend to join his new team-mates for pre-season training.
He will wear the No.18 shirt for City.
Capped six times by England, Delph began his senior career at Leeds United, making 50 appearances between 2006 and 2009.
In 2009 he was voted the Leeds United Young Player of the Year and Leeds United Players’ Player of the Year; he was also named in the PFA League One Team of the Year as well as winning the Football League Player of the Year to cap a memorable campaign for the Lilywhites.
Widely regarded as one of the brightest talents outside the Premier League, he moved to Aston Villa in 2009 for an undisclosed fee, aged just 19.
He became an integral member of the first team, and was voted the club’s Player of the Year in 2013/14.
Having represented England at Under-19 and Under-21 level, he won his senior call-up against Norway in September 2014, and after signing a new deal with the Midlands outfit earlier this year, he was handed the captain’s armband by new manager Tim Sherwood.
During his time in the West Midlands, Delph made 128 appearances for Villa, scoring eight goals.
Manuel Pellegrini admitted he was delighted at Delph’s decision to join City. He said: “Fabian Delph is an excellent player, and I am looking forward to working with him.
“He has made a huge impact in recent seasons at Aston Villa, and is now one of the brightest young midfielders in the Premier League.
“Fabian has tremendous skill and energy, and the fact that he has become a regular member of the England squad is further evidence of his progress over the past few seasons. At just 25 years old, he still has his best years ahead of him.”
Watch out for an exclusive CityTV interview with Fabian later today.
Don't forget if you want to see Fabian up close and personal, he will join the rest of the squad at this year's City Live in August.Tickets are available
so don't miss out.