Here's a look at 21 players under 21 years old who are either enjoying the early days of stardom or on the cusp of it.
Portuguese youth international Leao had an outstanding 2018-19 campaign at Lille. He's one of three players born in 1999 or later to record eight or more goals in Europe's top five leagues, prompting AC Milan's reported €30-million bid.
Atlanta United stud Barco is a pint-sized dribbling whiz with swift dispatch and stellar off-ball sense who's worth every penny of the then-record $15-million fee. Europe beckons for the latest of Atlanta's astute exports.
The first American player to line up for PSG, Weah moved to Lille following a loan spell at Celtic in a move that will afford the teen heaps of playing time. Like Wilfried Zaha, Weah is the perfect foil alongside a central striker.
Despite Marseille's best efforts to tarnish the status of their players, Kamara is a well-rounded star-to-be who's shown poise and positional awareness beyond his years in a role that often magnifies callow shortcomings.
Alex Iwobi's deadline-day move signaled Arsenal's faith in Nelson. Lightning-quick and energetic, he excelled on loan at Hoffenheim where he became the third-youngest player in Bundesliga history to bag five goals.
A slick dribbler with a hammer of a left foot, Canadian footballing savior Davies is set for a breakthrough campaign at Bayern. Though he's best served as a left-wing, his ability to deputize at left-back won't hurt his chances.
Mexican international Lainez arrived at Real Betis amid doubts he had the physical attributes to survive in Europe. Hogwash, says the Tabasco-born star, whose low center of gravity and artistry in close confines are already elite.
Any Inter fan who says they'd do the Radja Nainggolan-Zaniolo swap again has been drinking paint. The latter has become a veritable star for both Roma and Italy thanks to a robust frame, tireless energy, and deceiving agility.
City teen Foden's career is perfectly encapsulated in an assessment from Pep Guardiola: "Foden is the most talented player I've seen," Guardiola said. "His only problem is sometimes his manager doesn't put him in the starting XI."
Italy's youngest-ever scorer in a competitive match, Kean was shipped to Everton for a €27.5-million fee to the shock of Juventus fans who'd pegged the versatile striker for stardom. It's still in the cards, only now on Merseyside.
Guendouzi's move to Arsenal from second-tier Lorient was a scouting triumph that bore immediate response in an area of need. Composed and always moving, the Frenchman provides a balance and source of intelligent passing.
The youngest player to debut in a competitive fixture for England, Hudson-Odoi shattered Chelsea's institutional ceiling for budding stars to make a senior bow last year and play a critical role in the Blues' European success.
Donnarumma is both the youngest 'keeper to ever appear in a Serie A match and the youngest to appear in a competitive fixture for Italy. He bounced back in a big way last year after a mercurial 2017-18 season and already has 142 league appearances for Milan.
Dribbling whiz Pulisic, the USMNT's youngest-ever captain, will have ample opportunity to live up to a €64-million price tag at Chelsea this season as the Blues struggle to paper over the cracks formed during a two-window transfer ban.
The first player born in the 2000s to make an appearance for Real Madrid, Vinicius can thrive anywhere across the front line but profits most on the left flank, creating countless goal-scoring chances with a varied skill set.
Football's next great center-back, Juventus signing and Golden Boy winner De Ligt is a tidy defender who can play a pass and chip in on set pieces, like the one that saw him become the youngest player to score in a UCL semifinal last year.
Alexander-Arnold played a principal role in Liverpool's European conquest as a source of pinpoint passes; the modest right-back is the youngest player to record three assists in a Premier League match. A legend in the making.
Bayer Leverkusen's youngest-ever debutant and goal-scorer, Havertz is a two-footed midfielder who's earned the Alleskonner moniker reserved for do-everything players short on faults. Germany's next world-class star.
If Atletico's preseason was any indication, Felix has already acclimated to life under Diego Simeone. The Portuguese teen's link-up play with Diego Costa has been stellar, as were his two goals in an August friendly against Juventus.
Sancho led Europe's top five leagues with 14 assists last season at Borussia Dortmund, making the Three Lions international the first Englishman to record that many helpers in a top-flight league since Frank Lampard in 2010.
One of just two players to record 30-plus goals in Europe's top five leagues last season - Lionel Messi being the other - PSG's Mbappe has a World Cup and six domestic trophies to show for a burgeoning career that will likely feature multiple Ballon d'Or distinctions.