Hamilton stripped of Spa win
McLaren star's Championship lead cut to two points
Penalty: Hamilton and new race winner Massa
Lewis Hamilton has been demoted from first to third place in the Belgian Grand Prix after being handed a penalty following his late duel with Kimi Raikkonen.
The defending World Champion led the majority of the race after polesitter Hamilton spun at the start of lap two at Spa-Francorchamps.
But rain which had fallen two hours before the start of the race returned during the closing laps, allowing the McLaren Mercedes driver the chance to close the gap once again.
Hamilton re-took the lead from Raikkonen at the La Source hairpin with two laps to go and then, as the rain worsened, both drivers spun - but managed to keep their cars going.
However, after momentarily regaining the lead, Raikkonen then slammed his Ferrari into a wall at Blanchimont corner, with Hamilton using that as a cue to slow his pace considerably and tip-toe round the final lap to the chequered flag.
But it was Hamilton's move at the Bus Stop Chicane at the end of lap 42 just prior to his pass at La Source which later attracted the interest of race stewards.
Hamilton tried to pass Raikkonen under braking but instead straightlined the chicane. Emerging in the lead, he briefly let the Ferrari back through.
Nevertheless, about two-and-a-half hours after the race had finished, the Englishman was handed a 25-second penalty.
Hamilton's demotion means that Ferrari's Felipe Massa has now been handed the win, with Nick Heidfeld's late gamble on wet tyres paying off as the BMW Sauber driver moved up to third place on the track.
Fernando Alonso finished fourth for Renault, ahead of Toro Rosso's Sebastian Vettel and BMW Sauber's Robert Kubica.
Toro Rosso's Sebastien Bourdais finished seventh, with Red Bull's Mark Webber claiming the final Championship point.
Timo Glock had finished eighth on the track but the Toyota driver was also handed a 25-second penalty for making an illegal move on the Australian driver.
The race was pretty much a 'must win' for Raikkonen, whose chances of successfully defending his title have been slipping away throughout the summer.
Without a win since the Spanish Grand Prix at the end of April, he nevertheless came to Spa in the knowledge that he had won there three times in a row.
And for the majority of the race's 44 laps it appeared as though Raikkonen would extend his dominant run.
With Hamilton leading off the line on a damp track, McLaren team-mate Heikki Kovalainen made an awful start, the Finn dropping down from third place to 13th.
Massa also slithered wide at La Source, allowing Raikkonen up to second and when Hamilton spun at the same corner one lap later, the opportunity to take the lead presented itself.
Although Hamilton initially regained the lead, Raikkonen's momentum was such that he had caught the McLaren through Eau Rouge, before making the pass round the outside into Les Combes.
He edged away to build a lead that stood at 5.8 seconds by half-distance, but Hamilton managed to close the gap when both drivers made their second and final pit stops at the end of lap 25.
With both cars now running on harder compound tyres, Hamilton suddenly appeared to have the edge and Raikkonen's lead came down to 1.8s with 13 laps to go.
But for the gathering clouds, Raikkonen would likely have held on for a victory which would have given his Championship challenge renewed momentum.
Instead, he fell victim to what appeared a lottery - the inability of the current breed of F1 car to handle extreme conditions writ almost comically large as the World's best drivers were suddenly made to appear mortal.
As the rain started to fall, Hamilton homed in on Raikkonen and committed the move for which he was later penalised.
Forced to hand the lead back to his rival, Hamilton soon darted past again at La Source, with chaos predictably ensuing as the conditions worsened.
All of a sudden cars seemed to be spinning left, right and centre and, trying to avoid Nico Rosberg's spinning Williams, both Hamilton and Raikkonen lost and regained the lead once more before the latter's shunt.
Despite Raikkonen's late retirement, Ferrari still lead the Constructors' Championship over McLaren after Kovalainen failed to finish.
The Finn's afternoon hardly improved after his tardy getaway and, attempting to climb back through the field, he received a drive-through penalty after a collision with the sixth-placed Webber on lap 11.
Sunday's amended result means that, with five races remaining, Hamilton now leads Massa by just two points in the Drivers' Championship, with Kubica climbing to third place, albeit 22 points off the pace.
Raikkonen now stands fourth, one point adrift of Kubica, and, more crucially, 17 points behind Massa: will Ferrari now decide to throw their full support behind the Brazilian?
Belgian Grand Prix, result:
1. Felipe Massa (BRA) Ferrari 1hr 22min 59.394sec
2. Nick Heidfeld (GER) BMW-Sauber at 09.383sec
*3. Lewis Hamilton (GBR) McLaren-Mercedes 10.539
4. Fernando Alonso (ESP) Renault 14.478
5. Sebastian Vettel (GER) Toro Rosso-Ferrari 14.576
6. Robert Kubica (POL) BMW-Sauber 15.037
7. Sebastien Bourdais (FRA) Toro Rosso-Ferrari 16.735
8. Mark Webber (AUS) Red Bull-Renault 42.776
*9. Timo Glock (GER) Toyota 67.045
10. Heikki Kovalainen (FIN) McLaren-Mercedes 1 lap
11. David Coulthard (GBR) Red Bull-Renault 1 lap
12. Nico Rosberg (GER) Williams 1 lap
13. Adrian Sutil (GER) Force India-Ferrari 1 lap
14. Kazuki Nakajima (JPN) Williams-Toyota 1 lap
15. Jenson Button (GBR) Honda 1 lap
16. Jarno Trulli (ITA) Toyota 1 lap
17. Giancarlo Fisichella (ITA) Force India-Ferrari 1 lap
18. Kimi Raikkonen (FIN) Ferrari 2 laps
r. Rubens Barrichello (BRA) Honda 25 laps
r. Nelson Piquet (BRA) Renault 31 laps
(rank: r = retired, nc = not classified)
*25 second penalty
Fastest Lap: Kimi Raikkonen, 1:47.930, lap 24.