Chelsea have signed Benfica's Argentina midfielder Enzo Fernandez for a British record 121m euro (£107m) transfer fee.
The deal eclipses the £100m Manchester City paid for Jack Grealish in 2021.
Fernandez, who only joined Benfica for a reported £10m in August, was named young player of the tournament during Argentina's World Cup triumph in Qatar.
The 22-year-old's arrival takes Chelsea's January spending to £289m, according to transfer website Transfermarkt.
He has signed an eight-and-a-half year contract at Stamford Bridge.How can Chelsea keep spending?
The deal follows an outlay of £270m in the summer - a record for a British club in the summer window.
It is the joint-sixth most expensive signing of all-time, equalling the 120m euros Barcelona paid for France forward Antoine Griezmann in 2019.
Fernandez, signed by Benfica from Argentine side River Plate, has scored four goals in 29 appearances for the Primeira Liga side.
Benfica confirmed on Tuesday night that River Plate will earn 25% of the transfer fee, around 30m euros.
He scored once during the World Cup, netting Argentina's second goal in their 2-0 group-stage win over Mexico.
Earlier in January, Benfica accused Chelsea of trying to unsettle the midfielder, with the Portuguese side's manager Roger Schmidt declaring their pursuit "closed".
Chelsea have signed Noni Madueke, Mykhailo Mudryk, David Datro Fofana, Andrey Santos, Benoit Badiashile and Malo Gusto on permanent deals in January.
They have also brought in Joao Felix on loan from Atletico Madrid.
The Blues are 10th in the Premier League, 10 points adrift of the competition's Champions League places after 20 matches.
The club was bought for £4.25bn by a consortium led by American investor Todd Boehly last May, after previous owner Roman Abramovich was sanctioned over his links to Russian president Vladimir Putin.Head to our transfers page for all the latest done dealsVisit our Chelsea page for all the latest Blues news, analysis and fan viewsYou can now get Chelsea news notifications in the BBC Sport app - find out moreTransfer Deadline Day: Chelsea signings could be difficult for Graham Potter
World's top transfer fees
Neymar [Barcelona - Paris St-Germain] £200m in 2017
Kylian Mbappe [Monaco - Paris St-Germain] £166m in 2017
Philippe Coutinho [Liverpool - Barcelona] £142m in 2018
Ousmane Dembele [Borussia Dortmund - Barcelona] total fee of £135m in 2017
Joao Felix [Benfica - Atletico Madrid] £113m in 2019
Antoine Griezmann [Atletico Madrid to Barcelona] £107m in 2019
Enzo Fernandez [Benfica to Chelsea] £107m in 2023
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