The 2008 Fiat Yamaha MotoGP rider needed to score just five points in Malaysia, even if nearest rival Andrea Dovizioso won the race, but the Fortuna Aprilia star wanted much more and took the lead from Dovi at the halfway mark.
The Italian responded and remained in Lorenzo's slipstream, and the pair were then caught by KTM team-mates Hiroshi Aoyama and Mika Kallio - with Hector Barbera also in tow!
The top five exchanged blows until the penultimate lap, when class rookie Kallio launched an over-optimistic out braking move into the final hairpin - and took out race leader Dovizioso. That allowed Aoyama to inherit a lead he held to the finish, while Barbera took second place ahead of countryman Lorenzo.
Lorenzo celebrated his final 250cc title by changing into a gold-coloured boxer's dressing gown and gloves before a tearful Jorge 'danced' his way into parc ferme to collect a mock championship belt!
Kallio recovered to finish fourth, with former 125cc rival Thomas Luthi fifth after challenging Dovizioso and Lorenzo in the early stages. A distraught Dovi remounted to cross the line eleventh on a day when Aspar Aprilia riders Alvaro Bautista and Alex de Angelis both failed to finish.
Race results – Sepang:
1. H. Aoyama (KTM)
2. Barbera (Aprilia) +2.251secs
3. Lorenzo (Aprilia) +2.957secs
4. Kallio (KTM) +2.965secs
5. Luthi (Aprilia) +7.305secs
6. Simon (Honda) +8.747secs
7. Locatelli (Gilera) +16.105secs
8. Simoncelli (Gilera) +26.101secs
9. Takahashi (Honda) +28.032secs
10. Espargaro (Aprilia) +34.754
17. Laverty (Honda) +53.468secs