Earlier on Tuesday, Blues manager Roberto Mancini expressed his confidence the suspension would be overturned on the basis that Kompany did not foul Nani at the Etihad Stadium.
But an Independent Regulatory Commission has on Tuesday afternoon reached a different conclusion, ruling Kompany out of Wednesday night's Carling Cup semi-final with Liverpool.
"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."
In addition to Wednesday night's Carling Cup semi-final first leg, Kompany will also miss the return at Anfield in a fortnight, plus the Premier League encounters with Wigan and Tottenham in between.
Although opinion was divided about Chris Foy's decision to send Kompany off just 12 minutes into what was eventually a thrilling 3-2 defeat, once the decision was made, it always seemed unlikely to be overturned.
Sir Alex Ferguson and Wayne Rooney were in no doubts, with Mancini blaming the United striker for gesturing towards Foy in the immediate aftermath of the incident, for which, admittedly, Nani did not complain.
Mancini now faces the consequences, which is likely to mean the biggest match to date of Stefan Savic's short City career unless the Blues manager opts to select Micah Richards in central defence alongside Joleon Lescott as Kolo Toure is currently away on African Nations Cup duty.
"My opinion has not changed," said Mancini at his pre-match press briefing earlier on Tuesday.
"I am confident because Vinny only played 10 minutes.
"He was sent off for nothing. He has already missed one game.
"I don't think about this (being banned). It would be not correct if that happened."
Mancini also claimed he was right to point out that Wayne Rooney gestured to referee Chris Foy for Kompany to be sent off, even though the United star claims to only have been pointing out it was a two-footed tackle.
"I joked with Wayne Rooney. But he did it," said Mancini.
"Nani was there. He didn't say anything."
