Kylian Mbappe's decision not to take up the option of a 12-month extension on his Paris Saint-Germain contract could spark a bidding war for the French superstar this summer.

PSG is adamant he will not be allowed to leave as a free agent when his current deal runs out at the end of next season, meaning he could be put up for sale during this transfer window if a resolution over his future is not agreed.

Real Madrid has coveted Mbappe for a number of years and in 2021 unsuccessfully launched a bid of $190 million to take him to the Bernabeu. The Spanish giant would appear to be the likeliest destination for the World Cup-winning forward — especially at a time when it needs to find a replacement for Karim Benzema, who has joined Saudi Arabian team Al-Ittihad.

But Mbappe has this week described reports claiming he wants to move to Madrid this summer as “lies.”

“I have already said that I will continue next season at PSG where I am very happy,” he tweeted.

PSG will be put in a difficult position if Mbappe sticks to his current stance that he will not leave this summer and also will not sign a new contract.

The Qatari-backed French club has already seen Lionel Messi walk away as a free agent, after the Argentine great agreed to join MLS team Inter Miami, and would likely miss out on one of the biggest transfer fees in the history of soccer if Mbappe leaves for nothing as well.

Madrid is unlikely to be the only major European club interested in Mbappe, but his price tag means only a select few could afford to fund the deal.

Here's a look at other star players who could be on the move.

HARRY KANE (TOTTENHAM)

England's all-time leading goal-scorer is entering the final year of his contract and continues to be linked with moves to Manchester United and Madrid.

Tottenham has resisted all previous attempts to lure its iconic striker away but faces the risk of losing him for nothing if he refuses to extend his current deal.

Kane has never won a major trophy and turns 30 before the start of next season.

Spurs also know this summer may be the last chance to command a big fee for Kane, and reportedly value him at $123 million.

It remains to be seen whether Madrid's reported interest cools in light of Mbappe's potential availability.

In addition, that could also mean PSG is in the market for a new striker this summer.

ILKAY GUNDOGAN (MANCHESTER CITY)

Fresh from lifting the Champions League trophy in Istanbul, City's inspirational captain is set to become a free agent, unless a new contract can be agreed soon.

Gundogan has repeatedly been linked with a move to Barcelona, but City manager Pep Guardiola has made it clear that he wants the 32-year-old midfielder to stay.

Having completed the treble — including the Premier League title and FA Cup — this season, it might be the perfect time for the Germany international to say farewell.

DECLAN RICE (WEST HAM)

After seeing his England midfield partner Jude Bellingham sign for Madrid, Rice is also expected to be on the move this summer.

Arsenal appears to be leading the race for his signature, despite the midfielder also being linked with Manchester United, Chelsea and Bayern Munich.

An all-action midfielder, Rice would be a statement signing for Arsenal after the London club's Premier League title challenge collapsed in the final weeks of the season.

VICTOR OSIMHEN (NAPOLI)

The free-scoring forward has established himself as one of the most exciting strikers in the world and has picked up many admirers as a result.

Manchester United has been linked most heavily, given Erik ten Hag's need to bring in a top-class replacement for Cristiano Ronaldo, who left in November.

Osimhen might not be the only member of Napoli's league title-winning team who gets attention this summer — especially following the departure of inspirational coach Luciano Spalletti.

Khvicha Kvaratskhelia was outstanding last season, while defender Kim Min-jae is another player who has been linked with United.

JOSKO GVARDIOL (RB LEIPZIG)

One of the stars of the World Cup, the Croatia defender has been linked with a move to Manchester City.

However, Leipzig is expected to demand a world-record fee for a defender if it is to sell Gvardiol.

United paid 80 million pounds (then $97 million) for Harry Maguire in 2019.

Guardiola has already spoken of the need to build on City's Champions League success. Chelsea's Mateo Kovacic is another player City has been linked with.

Maguire, meanwhile, faces an uncertain future at United after losing his place under Ten Hag. He has been linked with a move to Tottenham.

MASON MOUNT (CHELSEA)

Chelsea has rejected a bid of around $51 million from United for the England midfielder, a person with knowledge of the offer told The Associated Press.

The person spoke on the condition of anonymity because they were not permitted to comment publicly.

Ten Hag has identified Mount as one of his top targets this summer as he looks to add more depth to a squad that won the League Cup and finished third in the Premier League last season.

But, with a top striker his priority, he is limited to how much he will able to spend elsewhere and it remains to be seen if United will go as high as Chelsea's reported valuation of around $89 million.

Along with Tottenham, United has also been linked with Brentford goalkeeper David Raya.

Mount has previously been linked with Liverpool and Arsenal.

RANDAl KOLO MUANI (EINTRACHT FRANKFURT)

The France striker impressed at the World Cup but was only in the squad as a late injury replacement before seizing his chance to shine.

He's long been seen as a target for Bayern Munich as the German champion has looked short of a center-forward since Robert Lewandowski left last year, but PSG and Manchester United have also been reported to be interested.

Kolo Muani scored 23 goals and set up 17 more in his single season with Frankfurt, which only qualified for the Europa Conference League next season.

MOISES CAICEDO (BRIGHTON)

Perhaps if Arsenal had been successful in its attempts to land Caicedo in January, it would not have fallen away so dramatically late in the season.

The midfielder has established himself as a stellar talent and looks certain to leave Brighton this summer.

Arsenal continues to be linked, along with Chelsea, while many more are likely to monitor his situation.