"I'm thrilled to have signed for Manchester City.
"When I learned of City's interest my heart was set on coming here and things have moved very quickly.
"I have loved my time with Borussia Dortmund and I would like to thank the club and the supporters for the five very happy years I spent there.
"They gave me a platform to play on and I became a better player because of the belief, patience and trust they showed in me.
"Now I have a new challenge and that is to achieve great things with City. The opportunity to work with a coach like Pep Guardiola is something I am really looking forward to and I am flattered to be the first signing the club has made this summer.
"I can promise the City fans I will give everything to help us win titles both in England and the Champions League. These are exciting times.
"I have my best years ahead of me and I think we can achieve great things together. I can't wait to begin this new chapter in my career."
Manchester City have announced the signing of midfielder Ilkay Gundogan from Borussia Dortmund.
The Germany international, who is ruled out of Euro 2016 due to a knee injury, becomes new City boss Pep Guardiola's first signing since taking over from Manuel Pellegrini.
The 25-year-old confirmed the four year deal in a video posted on City's official Twitter feed.
Manchester City left-back Aleksandar Kolarov faces a fitness test ahead of Sunday's final Barclays Premier League game of the season at Swansea.
The Serbia international missed last weekend's draw with Arsenal with a muscular injury and will be examined but captain Vincent Kompany (thigh), playmaker David Silva (hamstring) and right-back Pablo Zabaleta (calf) are all missing.
Midfielder Samir Nasri is back in contention after recovering from the illness which prevented him playing a full part in training last week.
Provisional squad: Hart, Caballero, Sagna, Otamendi, Mangala, Demichelis, Clichy, Kolarov, Toure, Angelino, Fernando, Fernandinho, Toure, Delph, De Bruyne, Sterling, Navas, Nasri, Aguero, Bony, Iheanacho.
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They're one of the world's biggest football clubs and now they're helping young fans stay in shape.
Manchester City hope they've come up with a winning formula to help improve the health of the region's children. As well as special free training sessions, children and parents in the community are invited to take part in healthy cookery classes.
It's proved to be a huge success and has been welcomed as figures show around 24% of children in Manchester will leave primary school obese.
Find out more about City in the Community here.
Manuel Pellegrini believes the best way for him to bow out at Manchester City is by winning the Champions League.
The Chilean is stepping aside as manager at the Etihad Stadium to make way for Pep Guardiola at the end of the season.
Pellegrini has won three trophies in his three years at the club and wants to add another.
City will hope to secure a place in the quarter-finals for the first time on Tuesday night as they take a 3-1 aggregate lead into the second leg of their last-16 tie against Dynamo Kiev at Eastlands:
Manchester City are on the brink of their first ever Champions League quarter final place heading into their game with Dynamo Kiev.Read the full story ›
Manchester City boss Manuel Pellegrini has confirmed Raheem Sterling will play in tomorrow night's Premier League clash at Liverpool.
It will be the first time he's appeared at Anfield since his departure last summer.
Sterling joined City in a £49 million transfer after refusing to sign a new deal with Liverpool. He was booed throughout Sunday's League Cup Final against his old club at Wembley. But his manager says he can handle an Anfield return.