Arsenal have completed the signing of Uruguay international Lucas Torreira from Sampdoria, the Premier League club have announced.
Torreira, 22, becomes Arsenal's fourth acquisition since Unai Emery was appointed as head coach in May.
The defensive midfielder has cost the Gunners a reported £27m and follows Stephan Lichtsteiner, Bernd Leno and Sokratis Papastathopoulos in joining the north London club this summer.
The club announced the signing this afternoon, with Emery delighted to add Torreira to his squad.
"In Lucas Torreira, we have signed a young player who is a very bright talent in the game," Emery told Arsenal's official website.
"A midfielder with great quality, I have enjoyed watching his performances for Sampdoria in the past two seasons, and we all saw him do very well for Uruguay in the World Cup.
"He is a young player already with good experience, but who wants to keep on growing. We welcome Lucas to Arsenal and look forward to him joining us soon for pre-season."
The length of Torreira's contract was not disclosed by Arsenal.
Torreira played a part in all of Uruguay's World Cup matches and started their quarter-final defeat to France last Friday.
With midfielders Jack Wilshere and Santi Cazorla released at the end of their contracts, Torreira's addition will be seen as key for Emery to bolster his numbers in the middle of the park.
As well as bringing in a quartet of new signings, Arsenal have extended the contracts of Calum Chambers, Ainsley Maitland-Niles and Granit Xhaka in recent weeks, while Mohamed Elneny has also agreed to fresh terms since Arsene Wenger stepped aside at the end of last season.