Manchester City destroyed Manchester United as Manuel Pellegrini sampled his first derby day in the North of England.
Sergio Aguero opened the scoring in the first half with a hooked finish before Yaya Toure doubled the lead with a tap-in just before the break.
The hosts made it three just a minute into the second half as Aguero volleyed home after great work from Alvaro Negredo, and Samir Nasri sealed it with a back-post effort.
Wayne Rooney scored a sensational 25-yard free kick in the closing minutes to put United on the board, but it did little to mask the mauling.
City started in ferocious form, seizing the initiative quickly and pushing their counterparts back into their own third.
The home crowd, loud and proud, roared their side into early dominance as United sank deeper and deeper, and the opening goal arrived after just 15 minutes.
Scintillating buildup play saw Samir Nasri corner Chris Smalling, feed Aleksandar Kolarov on the overlap and the Serbian fizzed in a drilled cross.
It was slightly behind Aguero, but the diminutive Argentine did a stunning job of hooking a firm finish into the far corner—David De Gea rooted to the spot.
Straight from kick off, City amped up the pressure once more, and the common theme for the half was final-third dominance from the home side interspersed by sporadic United counters.
Very little quality from David Moyes' midfield—in creating turnovers or in possession—meant the forwards were feeding off scraps. Wayne Rooney did his level best to spark something, but Danny Welbeck cut a borderline useless figure in attack.
The scoreline was doubled just before halftime, as City earned a corner, Alvaro Negredo flicked it on and Toure popped up for a tap-in at the far post. A dejected visiting side sloped into the changing rooms at the half, while the hosts left to a standing ovation.
Whatever halftime team talk was dolled out by Moyes became immediately redundant as Aguero grabbed his second, and City's third, just a minute into the second period.
Samir Nasri slotted Negredo in on the byline, and after expertly holding off Nemanja Vidic, clipped a cross into the box for Aguero to volley home. The Argentine had sniffed out the chance 22 yards from goal, and Marouane Fellaini failed to follow his marker.
Tom Cleverley was immediately sent on for Ashley Young, but City struck again to make it four before 50 minutes had even elapsed. Another volley, and this time it was Nasri converting after a cross from Jesus Navas and superb work from Vincent Kompany.
United eventually found their feet around the 60-minute mark, and Rooney spurned a great chance to peg the hosts back from 10 yards. Fellaini then had a strong effort saved by a sprawling Joe Hart, and Antonio Valencia made good ground in his one vs. one battle with Kolarov.
Pellegrini locked up the three points by adding fresh legs to the mix, and Rooney converted a stunning 25-yard strike late on to reduce the deficit.
Key Player Grades
Sergio Aguero, Manchester City, A
The Argentine oozed class, both in finishing and in his buildup play. An absolutely fantastic effort from the City forward.
Marouane Fellaini, Manchester United, D
United have lost the midfield battle every year since City emerged, and Fellaini did a horrific job coping with Yaya Toure's dominance.
Full Player Grades
City host Wigan Athletic in the League Cup midweek before travelling to Villa Park next weekend, while United must welcome Liverpool to Old Trafford on Wednesday before hosting West Bromwich Albion three days later.