England hooker Dylan Hartley has been given a four-week ban for headbutting and will be unavailable for the first game of the World Cup.
The Northampton captain, cited for a clash with Saracens' Jamie George, has already been warned about his behaviour by England coach Stuart Lancaster.
He will now have to serve the sixth suspension of his career with the ban running from 15 August to 21 September.
Hosts England start their World Cup campaign against Fiji on 18 September.
Hartley had pleaded guilty to striking George with his head during his side's Premiership semi-final defeat by Saracens on Saturday.
Disciplinary committee chairman Sean Enright said: "There cannot be any place in our game for this class of behaviour, and that is why we have imposed this sanction."