Sunderland have signed Wales international Adam Matthews from Scottish champions Celtic for £2m on a four-year deal.
Full-back Matthews, 23, joins defender Sebastian Coates at the Stadium of Light to become Dick Advocaat's second signing since returning to Wearside.
The former Cardiff defender won four Premiership titles at Celtic Park, and has 12 caps for Wales.
"Adam is a welcome addition to our squad," Advocaat told the club website.
"We know that we need quality players to improve competition for places in the side."
Matthews made close to 150 appearances in his four years with Celtic, scoring five goals.
On his departure, Celtic boss Ronny Deila said: "One year left on his contract, a good offer, and he wanted to try something else.
"It was the right time to do it."
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