Haynesworth was punished for unnecessary roughness against Andre Gurode of Dallas in the Titans' 45-14 loss to the Cowboys on Sunday.
After Cowboys running back Julius Jones scored on a five-yard touchdown run in the third quarter, Haynesworth stomped on the head of Gurode, who had lost his helmet.
A flagrant personal foul was called on Haynesworth and he was ejected from the game. Gurode needed nearly 30 stitches to close a gash on his forehead and beneath his eye.
The suspension is the largest in NFL history. Previously, Green Bay Packers defensive lineman Charles Martin was suspended for two games after slamming Chicago Bears quarterback Jim McMahon in November of 1986.