Manchester United trail neighbours City 22 points to 20 at the top of the Premier League, with City having the slight edge with a superior goal difference of plus-two.
The stakes could not be higher going into the first Manchester derby of the season, at Old Trafford on October 23, with City now a genuine title threat.
Here is a look at 10 games that define the rivalry.
In what was to be the last derby meeting between the sides before the Munich Air Disaster, United thumped City 4-1 at Old Trafford, showing what could have been had their fate not been decided in February 1958.
United legend Denis Law, now with City, condemned United to the second tier of English football after a back-heel from six yards found the net.
However, Law was inconsolable after scoring the goal, which helped send United down, and he couldn’t even celebrate. To this day, he regrets scoring against the club he loves so much.
This game was marred by crowd trouble after some United fans gained entry to the City-only end. The referee stopped the game, and it took 10 minutes before the teams came back out, but it didn’t stop both teams endlessly attacking.
City opened the scoring with David Oldfield driving his shot past Jim Leighton in the United goal. Trevor Morley doubled City’s lead after a scramble and poked home from three yards.
City’s third came after Oldfield clipped in an inviting cross that Ian Bishop duly headed home, giving the home side a 3-0 lead at halftime.
United pulled one back in the second half, and what a goal it was: Mark Hughes showed why he was one of the best strikers in England at the time with a wonderful scissor-kick that flew in off the crossbar.
It was to be United’s only consolation, as Oldfield got his second and City’s fourth with a tap in, and Andy Hinchcliffe added another to put Alex Ferguson in trouble of the sack, with supporters chanting “Fergie Out” throughout the drubbing.
United exacted revenge for the 1989 drubbing in 1994, showing the massive gulf in class between the two with a 5-0 annihilation.
Eric Cantona opened the scoring, and Mark Hughes added another, while it was a night to remember for Ukrainian winger Andrei Kanchelskis, who completed a hat trick. The winger ended the season as United’s leading scorer with 14 goals.
On 9 November 2002, City, managed by Kevin Keegan, won the last-ever derby at Maine Road 3-1.
Shaun Goater scoring his 100th and 101st goals for the club, and Nicolas Anelka scoring the other.
This was City's first win over United since the 5-1 victory in 1989, ending a 13-year barren run for the blue half of Manchester.
City came to Old Trafford looking for their first win at the stadium since 1974, and they duly obliged.
Both teams wore 1958 retro jerseys marking the 50th anniversary of the Munich Air Disaster, with away fans showing great honour to their club with their magnificent one minute of silence.
Those fans were rewarded, as goals from Darius Vassell in the 24th minute and Benjani in the 45th minute helped City to a famous derby win.
Michael Carrick got United’s consolation goal in the 90th minute, but City deservedly won this historic game.
Alex Ferguson claims this to be the best-ever Derby tie between the pair. Mark Hughes would beg to differ, as this result helped condemn his time in the City hot-seat.
Money-bags City came to Old Trafford smelling blood, but it was United who showed their hunger for victory, and that’s what won it for them.
City, which had goaded United fan’s with a giant poster of former United striker Carlos Tevez that read “Welcome to Manchester,” fell behind in the second minute through a Wayne Rooney strike.
Gareth Barry equalised 14 minutes later, a score line which the teams brought to the interval.
The second half was a real belter. Darren Fletcher gave United the lead four minutes into the half, only for City to equalise three minutes later with a goal from Craig Bellamy.
Nine minutes from time, Fletcher got his second and United’s third goal, which looked to be the winner, but their was still lots more drama to come.
Bellamy, who was brilliant on the day, grabbed a 90th-minute equaliser that looked to have given the visitors a share of the spoils.
But seven minutes of injury time provided lots of opportunities for both teams to grab victory, and it was United that did, with Michael Owen getting the winner in the 97th minute—queue the City protests.
It would have been typical of City to lose to either Bolton or Stoke in the final, yet they will always have this happy memory. This was a match they had to win to retain any sort of local pride, not to mention wider credibility after all the money that had been spent, and in the end they won it surprisingly convincingly.
This win led to City's first title in over 30 years.
The Manchester clubs were clawing for an advantage that would set the tone for a campaign in which they anticipated vying for all the major prizes.
This fixture had meaning, and United left satisfied after undermining their opponents' belief that they could resist the attacking power of Sir Alex Ferguson's team.
The victors could hardly demonstrate that more vividly than by rallying from 2-0 down to prevail 3-2 in injury time.
Paul Scholes' strike leveled this pulsating Carling Cup tie and gave the Old Trafford side the advantage on away goals.
Manchester United were good value for their lead, and they had Shay Given at full stretch on a number of occasions.
A Michael Carrick shot from six yards appeared to seal the victory with a quarter of an hour remaining. Then a Carlos Tevez strike took the tie to extra time. Finally, a goal from Wayne Rooney in injury time gave United the win.
United went on to claim the Carling Cup title.