Arsenal is set to sign Fabio Vieira from FC Porto in a deal worth up to €40 million, ESPN reports.
The 22-year-old will undergo a medical in London on Friday and put pen to paper on a five-year contract.
The Gunners will pay an initial €35m with a further €5m possible in performance-related add-ons.
Vieira has scored seven goals and provided 16 assists in 39 appearances for Porto and plays primarily as a No.10 or off the right flank.
He is yet to make a senior international appearance for Portugal but has featured 20 times for their Under-21s.
Vieira had a release clause of €50m but sources have confirmed Porto accepted a lower offer from Arsenal.