The 24-year-old German, defending champion and runaway leader of the 2011 championship, drove from pole to flag in flawless style in his Red Bull car. He won the floodlit 61-lap night race at the Marina Bay street circuit by a controlled 1.7sec.
Briton Jenson Button was second for McLaren to keep the title race just about alive with five races remaining. Australian Mark Webber in the second Red Bull was third.
Vettel now requires only one point to claim his second title in succession and can only be beaten to the title if Button wins all five of the remaining races and Vettel fails to score a further point.
Double World champion Fernando Alonso, who needed to finish on the podium to keep his own challenge for the Drivers' title alive, came home fourth ahead of Briton Lewis Hamilton in the second McLaren.
The Englishman produced a typically spectacular drive that included five pit-stops, a collision and a charge from 16th through the field.
nother Briton, Scotsman Paul Di Resta, was sixth for Force India, his best result in this his rookie season in F1, ahead of Germans Nico Rosberg in seventh for Mercedes and Adrian Sutil in the second Force India.
Felipe Massa of Ferrari, victim of a collision with Hamilton in the early stages of an incident-filled contest, was ninth. Mexican Sergio Perez, whose collision with Michael Schumacher saw the German eliminated from the race, finished 10th.
It was Vettel's ninth win this season and the 19th of his career. His Singapore triumph in sweltering humidity was heralded by an explosion of dazzling fireworks over the brightly lit cityscape.
Vettel won in 1hr59min6.757, a time that signalled the longest and most arduous race of the year. He, Button and Webber stood still, drained and dripping with sweat, on the podium at the end.
Vettel, from his 11th pole, pulled clear with apparent ease to take control early on, leaving the rest to scrap for places in a flurry of action into Turn 1, Sheares Corner and hardly looked back from there.
The brilliant German appeared to revel in his supremacy and opened up a comfortable lead as Hamilton, on successive laps, produced perfect passes to climb to sixth ahead of Rosberg and Schumacher.
By lap 11 Vettel was in cruise control as the rest battled furiously - Webber taking third from Alonso, whose rear tyres were very worn, Rosberg initiating the pit-stops and followed a lap later by Alonso.
Vettel's lead after 18 laps was more than 10sec. He stretched it to 20sec by lap 30 when the race was red-flagged for the first time after Schumacher ran into the rear of Perez's Sauber and made an airborne collision with the wall.
This brought out the pace car and signalled a spate of pit-stops while Schumacher's wrecked Mercedes was lifted clear. The 42-year-old German was not hurt.
Provisional full result of the Singapore 2011 Formula 1 GP
r Jaime Alguersuari (Spain) Toro Rosso +5 laps
r. Jarno Trulli (Italy) Lotus - Renault +14 laps
r. Michael Schumacher (Germany) Mercedes +33 laps
r. Timo Glock (Germany) Virgin +52 laps
Overall standings (after 14 races)