Derby County has reached an agreement to sign Poland international Bielik on a permanent deal.
The deal is reported to be worth £9.5million.
Bielik joined the North London based club in 2015 from Legia Warsaw.
The 21-year-old has been on the fringes of the Gunners all summer and a deal has been agreed to price away the centre-back.
Phillip Cocu, manager of Derby County has been an admirer of the former Charlton Athletic loanee.
Bielik impressed on loan at Charlton last season and is set to be named in Cocu’s squad for the opening game against Huddersfield on Monday.