With one match remaining, the duo are level on points, but a City win over Queens Park Rangers on Sunday would all but secure them the title.
United travel to Sunderland, but with City's vastly superior goal difference, Sir Alex Ferguson must call on a favour from former player and current R's boss Mark Hughes.
There have been many pulsating twists and turns in the battle for the title, and here Sports Mole picks out the pivotal moments from the campaign.
Man United 1-6 Man City, October 23
The 'noisy neighbours' were unbeaten at this point, but there were still doubts over their ability to get results when it really mattered. Not even the most loyal City fan could have dreamed of what followed at Old Trafford. The Citizens hit their biggest rivals for six in their own back yard. The message was loud and clear.
Basel 2-1 Manchester United, December 7
Among the disappointment of United's Champions League exit to Basel, they also lost their skipper Nemanja Vidic. The 30-year-old's damaged knee ligaments ruled him out for the season, and with it, United lost their driving force and the best defender in the Premier League.
Chelsea 2-1 Man City, December 12
Finally there were some cracks appearing in the City armour. Having taken the lead at Chelsea courtesy of a strike from Mario Balotelli, Mancini's side went on to lose 2-1 thanks to a late penalty from Frank Lampard. It was their first defeat of the season and set up an exciting festive period.
Christmas period, December 2011
United boss Sir Alex Ferguson has always maintained that the Christmas period holds much importance in the race for the title, and so it proved. City dropped points against West Bromwich Albion and Sunderland, but United passed up the opportunity to move clear with successive defeats to Blackburn Rovers and Newcastle United. Both teams remained in contention, but it was to be opportunities missed for either side.
Vincent Kompany banned, Yaya Toure unavailable
Among City supporters Kompany and Toure are viewed as key players. So when Kompany was suspended for the three games in January and Toure was called up to the African Cup of Nations by Ivory Coast, City's performances suffered. Kompany returned for Everton away, but Toure was still absent...
Manchester United 2-0 Stoke City and Everton 1-0 Manchester City, January 31
With City performing so spectacularly in the early part of the season, it seemed unthinkable that United would move level on points by the end of January. However, it happened on a Wednesday night in January when United scored two penalties against Stoke, and City stumbled to a 1-0 loss against a stubborn Everton team.
March was the month that for the first time, the title swung in favour of Man United. The Red Devils chalked up victories against Tottenham Hotsupr, West Bromwich Albion, Wolverhampton Wanderers and Fulham, while City slipped up against Swansea City, Stoke City and Sunderland. Heading into April, United's form looked ominous as they held a five-point lead over City.
That advantage was extended to eight points in United's favour as they defeated Queens Park Rangers at Old Trafford, while City slipped to a last-minute defeat at Arsenal, and it looked all over. However, City clocked up four straight wins, while United were left to rue costly lost points against Wigan Athletic, then they threw away a 4-2 lead against Everton, with the match ending 4-4.
Man City 1-0 Man United, April 30
What a difference a month makes! United were eight points clear of City earlier in April. However, a header from Vincent Kompany at the Etihad Stadium was enough to put the Sky Blues top of the table on goal difference with just two matches remaining. Mancini was adamant that United were still favourites though, with his side due to face in-form Newcastle United at the Sports Direct Arena.
Newcastle United 0-2 Manchester City, May 6
With 70 minutes on the clock, City were handing the title impetus to United as they remained level with Newcastle United. However, a late double from Yaya Toure drove Roberto Mancini's side into pole position. United managed a 2-0 win over Swansea City later in the day, but with one match remaining, City are firmly in the driving seat.