The left-back returns to the Stadium of Light after two years with the Hammers to become manager Roy Keane's 10th signing of the summer, joining the likes of Djibril Cisse, El-Hadji Diouf, and Northern Ireland team-mate David Healy.

McCartney told the club's official website, www.safc.com: "It's a great move for me and great to be back at Sunderland.

"The club has moved on over the last two years and I think there are exciting times ahead.

"The fans were always good to me and I hope that will continue and that we can have a good season.

"The club has changed a lot since I left but there are still a few familiar faces around, I can't wait to get going."

McCartney also told www.whufc.com he had personal reasons for returning to Sunderland: "I had two great seasons with West Ham," he said.

"I'd like to thank them for giving me the opportunity to play for a club with the history they have and their fantastic supporters.

"But for personal reasons alone, this move is right for me."

McCartney's capture concluded a busy day for Sunderland, with defender Danny Higginbotham returning to Stoke after only one season on Wearside.