The defender will be Mikel Arteta's first signing of the summer and provide cover for Kieran Tierney in what has been a problem area
Arsenal have agreed a deal with Benfica for Nuno Tavares, with the left-back set to undergo a medical with the Gunners ahead of a £7 million ($9.7m) transfer.
The two clubs have been locked in talks over Tavares for the past few days, with the Gunners keen to bring him in as cover for Kieran Tierney.
After a slight hitch in negotiations on Tuesday, a deal for the 21-year-old has now been reached.