Arsenal have completed the signing of midfielder Fabio Vieira from Porto in a £34.2m deal.
Porto released a statement on 17 June saying the Gunners would pay an initial £29.9m for the 22-year-old, with the rest in potential add-ons.
Arsenal have now announced Vieira has signed a long-term contract with them.
“I am very excited that we have identified and signed such a special talent,” said Gunners boss Mikel Arteta.
“Fabio is a very creative player that will bring high quality and versatility to our attacking play.”
Vieira has yet to win a senior cap for Portugal, but was voted player of the tournament at last year’s European Under-21 Championship.
He scored six goals and provided a league-high 14 assists in 27 Primeira Liga outings last season as he helped Porto claim the top-flight title in Portugal.
Vieira has become the Gunners’ third summer arrival, following USA goalkeeper Matt Turner and teenage Brazilian forward Marquinhos.