Arsenal have signed Belgium international Leandro Trossard from Brighton for £21m plus add-ons.
The 28-year-old forward’s contract runs until 2027 and has the option of being extended by a year.
He has scored seven goals and provided three assists in 16 top-flight games for Brighton this season.
“He knows the league here and I think he can have an immediate impact in the team,” Arsenal manager Mikel Arteta said.
The Gunners say they have submitted the required documents and hope Trossard will be available to face Manchester United at Emirates Stadium on Sunday (16:30 GMT).