United 2 // City 1
With his back to goal, England striker Rooney met a right-wing cross from Nani after 77 minutes with a perfectly-timed right-foot strike that flew into the top corner as City goalkeeper Joe Hart stood motionless.
Asked if it was his best goal, Rooney told Sky Sports later: "I think so, yeah. I saw it coming over and I thought why not? Nine times out of 10 they go into the stand."
Nani had given United a 40th-minute lead when he controlled Ryan Giggs' first-time pass before rolling a confident finish past Hart.
City equalised after 64 minutes when Shaun Wright-Phillips crossed for fellow substitute Edin Dzeko, whose shot went in off David Silva's back.
City deserved to be level with United, having more than held its own for most of the contest.
United manager Alex Ferguson sprung a surprise before kickoff by leaving top scorer Dimitar Berbatov on the bench, and playing Rooney on his own up front.
City counterpart Roberto Mancini also went for a lone striker in ex-United forward Carlos Tevez and his side should have been ahead after only three minutes when Tevez played in Silva, who shot inches wide of the far post from a close, but tight, angle.
Yaya Toure also threatened with a far-post header from a Gareth Barry free-kick, but, by the half-hour mark, Nani was starting to assert his influence and a Darren Fletcher header, from Giggs' cross, forced Hart into his first save of the game with 33 minutes gone.
Nani's goal, after Rooney had won an aerial challenge in midfield, sent United in at halftime with a 1-0 lead, but City started the second half in committed fashion with a Tevez run threatening and Silva, and Tevez again, shooting tamely at Edwin van der Sar.
Rooney, though, had the final say with only his fourth league goal of the season.
Arsenal 2 Wolves 0
Robin van Persie's double gave Arsenal a 2-0 victory over Wolverhampton on Saturday that kept the pressure on Manchester United in the title race.
The Netherlands striker struck either side of the break as the Gunners quickly recovered from last weekend's spectacular collapse at Newcastle when they surrendered a 4-0 lead to draw 4-4. Arsenal is four points behind leader Manchester United having played an extra game.
Birmingham 1 // Stoke City 0
Zigic headed in from close range off a cross from substitute Cameron Jerome to help Birmingham move further away from the relegation zone.
Birmingham won two straight league games for the first time in 14 months and has 30 points from 25 matches. Stoke has 33 points from 26 matches.
Liverpool 1 // Wigan Athletic 1
Midfielder Raul Meireles netted his fourth goal in five games from Fabio Aurelio's cross in the 24th minute.
But Wigan equalised when Steve Gohouri got the final touch on Antolin Alcaraz's flick, despite appearing to be in an offside position.
Liverpool had won four straight games in the Premier League under new manager Kenny Dalglish. The Reds remain sixth in the standings, while Wigan is third from bottom.
West Bromvich Albion 3 West Ham United 3
West Ham fought back from three goals down to draw 3-3 at relegation rival West Bromwich Albion. In front of new head coach Roy Hodgson, who was watching from the stands, West Brom scored twice in the opening eight minutes through Graham Dorrans and Jerome Thomas. Winston Reid's own goal put them 3-0 ahead before half time.
But Demba Ba scored twice in the second half for West Ham either side of Carlton Cole's header to secure the valuable point.
The point lifted West Ham off the bottom of the standings. West Brom is just two points further ahead and is only out of the drop zone on goal difference.
Blackpool 1 Aston Villa 1
Grandin headed in a Charlie Adam corner in the 14th minute, shortly after Gabriel Agbonlahor had given Villa the lead, sprinting through on goal, beating keeper Richard Kingson and slotting into the empty net.
Villa had Jean Makoun sent off in the 69th for a late challenge on DJ Campbell, but Blackpool could not make the one-man advantage count.
Villa brought on United States midfielder Michael Bradley for his debut in the 73rd minute and his new team came close to a winner when Ashley Young shot wide in injury time.