Happy days for champion Lorenzo
The Spaniard needed to come home ninth or better to clinch the championship on his Fiat Yamaha, helped by the absence of his closest rival and compatriot Dani Pedrosa due to an injury suffered in the last MotoGP round in Japan.
Reigning champion Valentino Rossi, a team-mate of Lorenzo at Fiat Yamaha, won the race in a time of 41 minutes 03.448 seconds, with Rossi's fellow Italian Andrea Dovizioso second for Repsol Honda.
Lorenzo started the race on pole and led through the first half of the race before the Italian duo went past him.
He said: "I was really impressed to be at the front and not to lose any time until the end of the race. But when the tyres started sliding I thought, 'today we have to finish the race and get the maximum a rider can get in the motorcycle world.'
"Today is the happiest day in my life and we have to celebrate it."
Casey Stoner endured a horrible day. The Australian crashed out on the final corner of the opening lap, but the race was an enjoyable experience for Rossi, who recovered from a poor start in which he dropped from sixth on the grid to 11th to win the race.
It was his first race success since victory in the opening round in Qatar six months ago – his longest run without a win in MotoGP in a season badly disrupted by the broken leg he suffered in the Italian Grand Prix.
Rossi said: "To get back to victory, and also to win this race, is very important for me. It makes me so, so happy."
Ben Spies was fourth on the Tech 3 Yamaha while series rookie Alvaro Bautista equalled his season's best performance by finishing fifth on his Rizla Suzuki.
Ryuichi Kiyonari was crowned British champion for the third time after the final round of the MCE Insurance British Superbike Championship at Oulton Park.
The Japanese rider finished on 649 points and his Australian team-mate Josh Brookes made it a one-two after he finished with 625 points.