Mark Webber beat Nico Rosberg to win the Monaco Grand Prix for the second time, and became the sixth different winner in six races in 2012.
Fernando Alonso joined Webber and Rosberg on the podium and now leads the drivers’ championship by three points from Vettel.
Sebastian Vettel also finished ahead of fifth-placed man Hamilton by starting the race on soft tyres and pitting late-on into the race.
Felipe Massa picked up his best result of the season by finishing sixth, and Force India celebrated a good day in Monte Carlo with Paul di Resta and Nico Hulkenberg finishing seventh and eighth.
Kimi Raikkonen picked up a couple of points for Lotus by finishing ninth, and Bruno Senna collected the final point.
Romain Grosjean retired after an accident in the first corner and both Michael Schumacher and Jenson Button retired towards the end of the grand prix just as some late afternoon rain was beginning to fall.
The skies were clear and the sun was beating down on the wealthy principality as the grid headed out on the formation lap. Tension was building nicely and, with so many potential winners at the sharp end of the grid, nobody could be sure what was going to happen off the start line.
Sebastian Vettel and Jenson Button, starting ninth and twelfth respectively, were starting the race on the soft tyres – the rest of the top thirteen had either opted for, or were forced by the regulations to use, the Pirelli supersoft tyre.
As the five red lights went out, Mark Webber got an excellent start off the line, and retained his lead. Behind him, however, chaos reigned. Romain Grosjean spun into the first corner. The Frenchman touched Fernando Alonso on his right, and then came across the track and clouted Michael Schumacher‘s right front tyre. Somehow, this did not do too much damage to the front suspension of the Mercedes, but it spun round Grosjean’s Lotus.
Kamui Kobayashi tagged the Lotus, which was momentarily strewn sideways across the track at the first corner. The Sauber driver became airborne briefly, and needed to head back to the pits at the end of that lap for some minor repairs. He did get back out on track, but had to retire a few laps later.
Pastor Maldonado, who started dead last, ran into the back of Pedro de la Rosa off the line. This ended the race for both drivers.
All this action brought out an early safety car, which stayed out until the end of Lap 4. Behind this safety car Webber led from Nico Rosberg, Lewis Hamilton was third and Fernando Alonso was fourth.
Once the safety car was back in, the race settled down into a bit of a procession as everybody seemed to be trying to conserve tyres, waiting for their first pit stops.
Jean-Eric Vergne was the first driver to make a scheduled pit stop at the end of Lap 17. Others, however, were holding off, expecting some rain to arrive within the next few laps.
Mixed messages were flying between the pit garages and various drivers about when the rain was going to come, and by Lap 25, those who had started on used supersoft tyres were starting to complain.
Mercedes were the first to blink, on Lap 28, as Nico Rosberg came in for a set of the Pirelli soft tyres. This decision left Red Bull and Mark Webber in a bit of a quandary – do they make their pit stop now to cover off the German, or do they rely on the rain coming, in which case Rosberg would have to make another stop anyway?
Webber did pit at the end of Lap 29, as did third-place man Hamilton. Fernando Alonso, who was sitting in fourth place, stayed out on track. Webber retained the lead of the race from Rosberg when he re-emerged from the pit lane.
Alonso pitted next time round, and had leap-frogged Hamilton to take up position behind Rosberg and Webber.
Sebastian Vettel was now leading the race, and making good use of the Pirelli soft tyres on which he had started. At the end of Lap 33, the world champion had a 13 second lead over his team-mate, and that lead was continuing to grow.
Michael Schumacher made his first pit stop at the end of Lap 34. Some good laps from the seven-time world champion allowed him to get past Kimi Raikkonen , who had been holding him up before the pit stops had begun, very easily.
Now only Vettel, Jenson Button and Daniel Ricciardo had failed to make their first pit stops. This was particularly impressive from Ricciardo, who had actually started the race on the less-durable supersoft tyres.
Button made his first and only scheduled stop on Lap 39, but came out behind Heikki Kovalainen, who he was racing with for position after a poor start to the grand prix. Ricciardo pitted a couple of laps later, leaving current race leader Vettel the only driver who had not made at least one stop.
Although there were a few spots of rain in the pit lane, there was no significant downpour for now, and teams finally stopped trying to second guess the weather and started to concentrate on their own strategies.
Vettel finally made his one and only stop at the end of Lap 45 of 78, just as his pace was beginning to drop below that of the following cars. Webber, Rosberg and Alonso all went through, but the German just made it out of the pits ahead of Hamilton.
At the end of Lap 50, 5.2 seconds covered the top 6 in the grand prix. Webber led Rosberg, then Alonso. Vettel on a fresh set of supersoft tyres was fourth, ahead of Hamilton and Massa. Seventh was Michael Schumacher, who was a further 22 seconds behind his former Ferrari team-mate.
Now it was just a question of whether anybody would have to stop again, and what Vettel could do on much fresher tyres at a track where it is ‘impossible’ to overtake.
Schumacher, who had been sitting pretty in seventh place, then began to report a problem with his car, a couple of laps later, and his lap times suddenly began to increase. He let Vergne through on Lap 62 and then, a couple of laps later, the Force India duo, led by Paul di Resta, where also allowed past. On the next lap, he drove into the garage to retire the car.
Meanwhile, the race looked set for a dramatic finish as Nico Rosberg started to gain on race leader Mark Webber, and umbrellas started to come out all around Monaco. The rain had finally arrived, albeit only light rain.
In the closing laps, Webber’s pace began to desert him, and Rosberg, Alonso, Vettel and Hamilton were now forming a train behind the Red Bull. Things were looking set for a close finish to the Monaco Grand Prix.
The frustration of Jenson Button, who had spent much of the race stuck behind Kovalainen, finally showed about 6 laps from the end when a hopeful move ended with him spinning near the swimming pool. The resultant damage left the McLaren driver out of the race.
Bizarrely, Jean-Eric Vergne made a late stop, and took on some intermediate tyres. This proved to be a gamble too far for Toro Rosso – the track was not wet enough and the Frenchman quickly began to drop down order.
There had been conversation around the paddock this morning about a technical infringement on the Red Bull car. Rumours were abounding that some teams are planning to protest the result and, with Webber taking victory, this could be all the more likely.