In an inaugural race delayed by a downpour, started, stopped again and then re-started behind the safety car after a 48 minute wait, the Spaniard could scarcely believe his good fortune and others' bad luck.
With two races to go, and a maximum 50 points to be won under the new scoring system, Alonso celebrated his fifth win of the year to turn a 14-point deficit into an 11-point lead over Red Bull's Australian Mark Webber.
McLaren's 2008 champion Lewis Hamilton finished second, 14.9 seconds behind, and moved up to third overall with 210 points, 21 behind Alonso.
Brazilian Felipe Massa was third for Ferrari.
Image: Ferrari Formula One driver Fernando Alonso of Spain, center, celebrates on the podium after winning the Korean Grand Prix, with second placed McLaren driver Lewis Hamilton of Britain, left, and third placed Ferrari driver Felipe Massa of Brazil at the Korean International Circuit in Yeongam, South Korea, Sunday, Oct. 24, 2010.