Arsenal have signed Benfica left-back Nuno Tavares in a deal worth around £8m.
The 21-year-old, who played against Arsenal in the Europa League last season, is the Gunners' first signing of the summer.
He made 25 first-team appearances for the Lisbon club and also been capped for Portugal under-21s.
"He is a young player with great promise who has developed very well," Arsenal manager Mikel Arteta said.
"Nuno's arrival will give the squad extra strength and options in defence, particularly with this energy on the left side of the pitch."
Meanwhile, Tavares says he's excited about the move.
He told the club's website: "I'm so excited because it is a big club and for me as a young guy, it is a pleasure to be here.
"It's good for my career and to begin at Arsenal is a big club, and I'm very happy.
"When I finished the season my agent told me that Arsenal were interested in me. In the first instance I was very happy and after this I dreamed about it, and [spoke about it] with my mum. I was so excited to be here, and now I'm here I'm so happy.
"It was not a quick process. There were more things about the contract, and with things between the clubs of Arsenal and Benfica. It was not quick, it took a long time, and the negotiations went not quickly."
