, in the last three months
Mbappe's value has risen an astronomical 37 per cent to £160.9million.
The 18-year-old has eight goals in 17 games since joining for a season from Monaco.
He is expected to sign a permanent deal with PSG in the summer for a fee more than £100m.
In second spot in the rankings is Tottenham midfielder Dele Alli , valued at £158.6m.
Dele Alli is attracting some interest from Europe's biggest clubs Credit: Getty Images - Getty Leroy Sane is in blistering form for Man City and is the third most expensive U21 player Credit: Getty Images - Getty This is actually a one per cent drop since September 1, but the 21-year-old continues to attract interest from Europe's biggest clubs, such as Manchester United and Barcelona.
In third spot is Manchester City winger Leroy Sane , valued at £109.6m.
The German international is in sparkling form, and despite Pep Guardiola having an embarrassment of riches in the midfield positions, Sane has become a regular.
Despite still being out injured, Barcelona attacker Ousmane Dembele is ranked as the fourth most expensive U21 talent.
Most Expensive U21 Players In The World
Kylian Mbappe (PSG) - £160.9m Dele Alli (Spurs) - £158.6m Leroy Sane (Man City) - £109.6m Ousmane Dembele (Barcelona) - £106m Marcus Rashford (Man United) - £102.7m Gabriel Jesus (Man City) - £98.5m Timo Werner (RB Leipzig) - £81.4m Anthony Martial (Man United) - £75.4m Christian Pulisic (Dortmund) - £66.2m Davnson Sanchez ( Spurs) - £58.4m Wilfred Ndidi (Leicester) - £57.1m Gianluigi Donarumma (AC Milan) - £49m Federico Chiesa (Fiorentina) - £46.3m Lorenzo Pellegrini (Roma) - £44.6m Marco Asensio (Real Madrid) - £44.6m Andreas Christensen (Chelsea) - £41.9m Franck Kessie (AC Milan) - £41.9m Youri Tielemans (Monaco) - £40.7m Daniel Ceballos (Real Madrid) - £38.6m Theo Hernandez (Real Madrid) - £37.7m The Frenchman joined the Catalans in the summer from Borussia Dortmund for £135.5m to soften the blow of Neymar leaving for PSG.
But he picked up a thigh injury that required surgery in early September, and is not expected back until early 2018.
Kylian Mbappe equalises for PSG against Strasbourg in Ligue 1 Ousmane Dembele, despite his current injury, is the fourth most expensive U21 player in the world Credit: Rex Features Manchester Untied attacker Marcus Rashford completes the top five of the best U21 players Credit: AFP
Manchester United ace Marcus Rashford and Anthony Joshua work out Completing the top five is Manchester United and England striker Marcus Rashford.
He is worth £102.7m, a whopping 28 per cent increase in value from the same time three months ago.
Elsewhere to note from the top 10 players, Wilfried Ndidi is apparently worth more than Real Madrid's top talent Marco Asensio.
Leicester man Ndidi weighs in at £57m, while Asensio is "only" rated as being worth £44.6m.
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