The 24-year-old has signed a four-and-a-half year contract with the Black Cats.
Sunderland boss Sam Allardyce told the club’s official website: “Wahbi is a quick, dynamic attacking player.
“He has many attributes, not least his delivery from wide areas and set pieces and of course his ability to score goals.
“His versatility will certainly complement our existing forward options and I am delighted to welcome him to the club.”
Khazri becomes the fifth new arrival at the Stadium of Light this month.