Arsenal have completed the signing of midfielder Fabio Vieira from Porto in a 40m euro (£34.2m) deal.
Porto released a statement on 17 June saying the Gunners would pay an initial 35m euros (£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.