beat McLaren team-mate Jenson Button to pole
at the Italian Grand Prix as Ferrari's Fernando Alonso bid failed.
Alonso, the world championship leader, had been quick all weekend but could manage only 10th because of a mechanical failure on his car.
Felipe Massa was third ahead of Force India's Paul di Resta,
who has a five-place gearbox change penalty.
Mercedes' Michael Schumacher was fifth from Red Bull's Sebastian Vettel.
Mercedes driver Nico Rosberg took seventh, ahead of Lotus's Kimi Raikkonen, Sauber's Kamui Kobayashi and Alonso.
Di Resta will be demoted to ninth, between the Sauber and the Ferrari.
It was a third pole in a row for McLaren, after
Hamilton started from the front in Hungary
Button did so in Belgium a week ago.
But the story was Alonso, who was 1.4 seconds slower in the top 10 shoot-out than he had been in setting the fastest time in the second part of qualifying. He was also fastest in the first part.
Ferrari had tried a strategy of getting their drivers to 'tow' each other around the track, but the tactic did not work.
Massa set his best time without the use of a tow, and Alonso was unable to use it because of his problem, which Ferrari said was "probably" a rear anti-roll bar failure.
It is a serious blow to the Spaniard, who heads into this race
with a 24-point championship lead,
a margin that was dramatically reduced by Vettel in Belgium following Alonso's retirement in a first-corner pile-up.
He said: "We miss the fight for pole with a failure. Tomorrow will be a perfect day to recover some positions."
Hamilton said: "I had much better laps in practice, but generally I can't complain. I didn't think that lap was anywhere near good enough.
Did you know?
Ferrari have won eight of the last 16 races at Monza. Six of the last 10 Italian Grands Prix have been won from pole.
"I had Kimi and the two Ferraris in front and I wasn't able to better it. I'm happy for the team because they have been doing a fantastic job. To have us both up here is what they deserve.
"It's a beautiful track, and the more you drive it you respect it more and more. Also the fans here are fantastic, great people who love motor racing. It's great to see."
Button added: "It's great for the team for us both to be on the front row. The last few races have really shown our strength. Even being on the front row it's not going to be an easy race."
Di Resta's team-mate Nico Hulkenberg was knocked out in the first session after his car stopped out on the track at the first chicane before he had recorded a timed lap.
"We suddenly lost drive, the engine just switched itself off," he said.
"It's quite disappointing, we showed good pace in the practice sessions and we could have had a good day today, but now it's a different challenge in the race.
"But I've certainly not given up and I think the car can still get me into the points."
Raikkonen's team-mate Jerome D'Ambrosio could manage only 16th place on a one-off appearance as a stand-in for
Romain Grosjean, who was banned for a race
for causing the Spa first-corner crash.
At the back of the grid, Narain Karthikeyan out-qualified HRT team-mate
Pedro de la Rosa
for the first time this season, on the occasion of the Spaniard celebrating his 100th grand prix.
Italian Grand Prix 2012, day two
- Saturday, 8 September: Qualifying highlights: 17:30-18:45; BBC One.
Italian Grand Prix 2012, day three
- Sunday, 9 September: Race: 13:00 BST; BBC Sport website text commentary and BBC Radio 5 live. Highlights 17:30-19:00; BBC One. Race highlights repeat: 0030-0200; BBC Two.