Abstract: A tensioner (10) for a seat belt includes a cylinder tube (12), a piston (14) that is movably arranged in the cylinder tube (12), a tension transmission means (24) connected to the piston (14) at a connecting portion (26) for transmitting the movement of the piston (14) to the seat belt, as well as a drive (18) which is adapted to exert a driving force in a tensioning direction A on the piston (14) so as to tension the seat belt. The tensioner (10) moreover includes a return stop which counteracts a displacement of the piston (14) in a direction B opposite to the tensioning direction A. The connecting portion (26) is arranged in the tensioning direction A ahead of the return stop.