David Moyes makes his fifth signing as the manager of the Black Cats as he brings in the former Dortmund, Everton and Tottenham Hotspur midfielder on a one year deal.
Sunderland announced the signing of midfielder Steven Pienaar on a deal until the end of the 2016-17 campaign.
The 34-year-old moves to the Stadium of Light after being released by Everton when his contract expired at the end of last season.
Pienaar made just four Premier League appearances last season after spending much of the campaign sidelined with a thigh problem.
The former South Africa international is David Moyes' fifth signing of the transfer window, following the arrivals of Papy Djilobodji, Adnan Januzaj, Paddy McNair and Donald Love.