The Germany international joined City in 2016 and was Pep Guardiola's first signing as Citizens boss.
He scored two excellent strikes against Manchester United in the FA Cup final to keep City's dreams of the treble well and truly alive.
But the Champions League final between City and Inter Milan could prove to be his final game for the club.
Gundogan's contract situation
The 32-year-old's deal at the Etihad expires at the end of June.
City were only willing to initially give him a one-year deal.
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However, after scoring crucial goals against Leeds and Everton in the Premier League run-in, the Citizens have offered a new contract that is much closer to what he was looking for.
Gundogan has become an integral part of a City side that could make history, so it's no wonder they want to keep him.
But the former Borussia Dortmund midfielder has refused to be drawn into any conversations about his future.
Speaking after the FA Cup final, he said: "I don't need these kind of days to feel appreciated and feel special in this club. Nothing is decided yet, so we're going to see what's going to happen."
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Where could he go?
Manchester City
City have now offered Gundogan a new two-year deal with the option of a further season.
But Gundogan's agent and father, Ilhan, has denied any suggestion that a contract extension has been agreed.
He said: "Nothing has been agreed with City or any other club.
"The recent reports are not true. Ilkay is only focused on the final."
Barcelona
The LaLiga giants are extremely keen on recruiting the ex-Dortmund star this summer.
Xavi's side initially offered Gundogan a two-year deal with the option of an extra year.
But reports in Spain suggest Barca have now tabled a three-year contract.
And this is thought to have swayed the odds in their favour.
Xavi was also very bullish when asked about Barcelona's chances of signing the City captain.
He said: "Well, the only thing I can share is that any footballer we are going to sign and that we have the chance to talk to wants to come here.
"I have not seen any player tell us 'no, I prefer to go to another club.'"
Arsenal
The Gunners are desperate for midfield reinforcements this summer, with Granit Xhaka set to leave.
And Mikel Arteta believes that Gundogan would be the perfect upgrade on Xhaka, and Arsenal are plotting a move for the midfielder.
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The two worked together at City for three years and the London giants are preparing to make an offer should Gundogan reject City's advances.
But with that situation on hold, Arsenal are unlikely to do anything.