- Riyad Mahrez (43' Pen, 61', 66')
After exiting at the semi-final stage for the last three seasons, Pep Guardiola's treble-chasing side were not about to suffer the same fate and won without requiring top gear.
Championship promotion hopefuls United began brightly and frustrated City for most of the first half but Mahrez fired City ahead from the penalty spot in the 43rd minute.
Mahrez then waltzed through some flimsy defending to make it 2-0 in the 61st minute and completed his hat-trick five minutes later with a clinical finish from Jack Grealish's low cross.
City have not conceded a goal in reaching the FA Cup final for a 12th time where they could face Manchester United in what would be the first all-Manchester clash in the showpiece.
United are up against Brighton & Hove Albion on Sunday.
City are also in the semifinals of the Champions League where they will face holders Real Madrid.
It proved a disappointing day for Sheffield United who last won the FA Cup almost 100 years ago, although the club's priority will be sealing promotion back to the top flight after being relegated in 2021.
- Stuart Attwell