The Gabon international becomes the seventh new face at the Stadium of Light since David Moyes took over as manager and is raring to begin his new challenge.
Sunderland has signed midfielder Didier Ndong from Ligue 1 side Lorient for a fee of 16 million euros ($17.84M).
The 22-year-old has agreed to a five-year deal on Wearside and becomes David Moyes' seventh signing since succeeding England boss Sam Allardyce as manager at the Stadium of Light.
Ndong, who has 18 caps for Gabon, told Sunderland's official website: "I am very proud and happy to sign for Sunderland.