Cape Town - Arsenal have completed the signing of 17-year-old midfielder Krystian Bielik from Legia Warsaw for an undisclosed fee, the club's website confirmed on Wednesday.
Bielik made his senior debut for the Polish club in August aged 16.
He went on to feature five times for Legia in the league and once in the Europa League.
The versatile Poland youth international can play in both holding midfield and at centre-back.
The deal is subject to the completion of regulatory processes.