Calum Chambers has joined Middlesbrough on a season-long loan from Arsenal.
The 21-year-old signed for Arsenal from Southampton in July 2014 and won the FA Cup with the Gunners in 2015.
Chambers has made 58 Premier League appearances and has three England caps to his name but the defender - who can play at right-back and in the centre - has been deemed surplus to requirements by Arsenal, who appear set to sign Shkodran Mustafi from Valencia.
The focus for Chambers switches to helping Middlesbrough retain their Premier League status following promotion from the Championship last season.
Middlesbrough head coach Aitor Karanka said: "I'm really pleased. It's a position where we've been working towards bringing the right player in.
"We haven't been in a hurry because Calum was the player we were waiting for, and he's going to help us a lot.
"I'd like to say thank you to him because we know he had another offer, but he wanted to come here. That's important and we're looking forward to working with him."