Arsenal have signed teenage midfielder Krystian Bielik from Legia Warsaw.
The Barclays Premier League club confirmed the move for the 17-year-old on their official website, with a fee in the region of £2.5million said to have been agreed.
Poland youth international Bielik, who also had talks with German club Hamburg, is expected to work initially within the Gunners' Under-21s side, with a view to a swift progression through to the senior squad.
A statement from Arsenal read: "Arsenal have completed the signing of 17-year-old midfielder Krystian Bielik from Legia Warsaw for an undisclosed fee."
Bielik, who made his senior debut for Legia at the age of 16, has made six appearances for the club, and can play in both midfield and defence.
Arsenal won 2-0 at Manchester City on Sunday to close back up on the top four of the Premier League.
Manager Arsene Wenger is determined to secure some more defensive cover in the January transfer window.
It is understood there has been contact with Villarreal over centre-back Gabriel Paulista, who is said to have a 20million euros (£15.25m) release clause.
The 24-year-old Brazilian would, however, require a work permit to play in England as he is not yet an established international.
FA Cup holders Arsenal travel to Brighton on Sunday, where the likes of Theo Walcott and Mesut Ozil could both start following injuries.
