Premier League - Kompany appeal rejected
The suspension is a major blow for the Premier League leaders, who will also be without centre-back Kolo Toure for the next few weeks while he is away with Ivory Coast at the African Cup of Nations along with brother and City team-mate Yaya.
Earlier on Tuesday, Blues manager Roberto Mancini expressed his confidence the suspension would be overturned, but an Independent Regulatory Commission has reached a different conclusion.
"An Independent Regulatory Commission has today [Tuesday 10 January] dismissed a claim of wrongful dismissal from Manchester City's Vincent Kompany following his red card for Serious Foul Play in The FA Cup Third Round tie between Manchester City v Manchester United on 8 January 2012," said an FA statement.
"Kompany will serve a four-match suspension with immediate effect.
"The suspension consists of a statutory three-match suspension for Serious Foul Play plus one additional game given this is Kompany's second dismissal of the season."
The 25-year-old will be available again for City's trip to face Everton in the league on February 1.