By Andrew Benson
BBC Sport at Monza
Vettel claimed his first F1 pole in treacherous conditions
Toro Rosso's Sebastian Vettel will start the Italian Grand Prix from pole at the head of a grid mixed up by rain during qualifying on Saturday.
Lewis Hamilton qualified 15th after a strategic error. His world title rival Felipe Massa is sixth and Massa's Ferrari team-mate Kimi Raikkonen 14th.
Hamilton was eliminated in the second session after going out on the wrong tyres when the track was at its driest.
Heikki Kovalainen was second, ahead of Mark Webber and Sebastien Bourdais.
The result sparked wild celebrations in the Toro Rosso pit, and will lead to expectations for a thrilling race as the front-runners try to work their way through the field.
Vettel, 21, replaces double world champion Fernando Alonso as the youngest man to take pole position in Formula One history.
"Unbelievable," he said. "Incredible. I was talking with my engineers and we said if it's wet we have to go for pole position.
"It was difficult. The most difficult part was the Ascari chicane, where there was so much water. I never dreamt of being on pole.
"I wasn't very happy with the car in the wet yesterday but we made some changes overnight and it was much better today. And when you are confident in your car it is much easier in the wet.
"There was no real secret. We did more or less the best we could in running out there. It always depended on the conditions.
"In the second session it was quite difficult. I set my time quite early, and it got wetter and wetter, so the ones who delayed going out had a bit of bad luck."
The forecast is for more wet weather on Sunday, and if correct it will be the first wet race at Monza since 2004, and only the fourth in the time the venue has hosted the Italian Grand Prix.
Webber said: "I don't think anyone wants to race in those conditions. There are some safety concerns at this place because of the high speed."
Hamilton and McLaren will be ruing their decision to go out on intermediate tyres at the start of the second elimination session.
The rain had briefly abated after the first session, but the track was too wet for intermediates, which are designed to work in drier conditions than the full wet weather tyres chosen by most of his rivals.
"I made the wrong decision on the tyres. It looked like it was either full wets or inters," he said, making a 50-50 sign with his hand.
"I just thought there was not that much standing water and by the looks of things it wasn't going to get wetter and if you can get the heat into the inters it should be quicker.
"But as soon as I went out it chucked it down. I came in, was weighed and missed the window when the track was quickest."
Hamilton should still have had a chance of making it into the top 10 - he was out at the same time as Massa but was nearly three seconds slower than the Brazilian.
But he said that the wet conditions meant he could not get his brakes and tyres to work properly.
We should not underestimate what Toro Rosso have done this year. They have been seriously fast in the last few races
"When I went out, I didn't get the tyres and the brakes heated up. I'd already glazed the brakes and I couldn't get the tyres up to temperature.
"Honestly, once you lose temperature with these tyres, there's nothing you can do. So I struggled from then on.
"I don't feel fantastic, but what can you do? You can always make mistakes. It's just a part of the learning curve.
"Everyone has ups and downs. It's just one of those days. You have to take it on the chin and keep pushing.
"You don't get points for today, you get points for tomorrow. Hopefully, Heikki can win the race and I can score some points."
Kovalainen said he was confident of a good result but that the Toro Rosso cars should not be discounted.
"We should not underestimate what Toro Rosso have done this year," the Finn said.
"They have been seriously fast in the last few races. We can't take anything for granted. But I'm feeling very confident.
"We were there all the time this weekend. OK, we didn't manage to nail pole, but the car is in good shape. We will try to win, but it won't be easy."
Italian Grand Prix qualifying result:
1 S Vettel (Ger) Toro Rosso-Ferrari 1min 37.555secs
2 H Kovalainen (Fin) McLaren-Mercedes 1:37.631
3 M Webber (Aus) Red Bull-Renault 1:38.117
4 S Bourdais (Fra) Toro Rosso-Ferrari 1:38.445
5 N Rosberg (Ger) Williams-Toyota 1:38.767
6 F Massa (Bra) Ferrari 1:38.894
7 J Trulli (Ita) Toyota 1:39.152
8 F Alonso (Spa) Renault 1:39.751
9 T Glock (Ger) Toyota 1:39.787
10 N Heidfeld (Ger) BMW Sauber 1:39.906
11 R Kubica (Pol) BMW Sauber 1:36.697
12 G Fisichella (Ita) Force India-Ferrari 1:36.698
13 D Coulthard (GB) Red Bull-Renault 1:37.284
14 K Raikkonen (Fin) Ferrari 1:37.522
15 L Hamilton (GB) McLaren-Mercedes 1:39.265
16 R Barrichello (Brz) Honda 1:36.510
17 N Piquet Jr. (Brz) Renault 1:36.630
18 K Nakajima (Jpn) Williams-Toyota 1:36.653
19 J Button (GB) Honda 1:37.006
20 A Sutil (Ger) Force India-Ferrari 1:37.417