The charges mean Keane didn't behave with the respect for the game that professional footballers are supposed to have.
The FA charged him after he admitted in his autobiography that he deliberately tried to hurt Manchester City's Alf-Inge Haaland in a vicious tackle 18 months ago.
The FA believe he wrote about the tackle so the book could make more money.
The ban will start on 4 November and Keane should be back for United's home Premiership game with Arsenal.
Keane can appeal - in other words ask the FA to rethink the punishment - but he only has 14 days to do so.