Competing in the all-Ford Fiesta Rally3 class, 24-year-old Korhonen started Sunday with a 52.6sec advantage after his closest rival throughout Friday and Saturday, William Creighton, faded out of contention when he dropped around one minute on Saturday afternoon.
There were no dramas for the young Finn, who cruised through the three-stage finale with victory in his sights. Ending on a high with the fastest Wolf Power Stage time, Korhonen's final winning margin was 39.6sec.
"This means a lot," he said. "It's my second WRC rally and my first time in Sweden, so I am really happy. It was a good fight with Creighton until he got some problems, but a good rally for us."
Creighton's Saturday woes had dropped the Irishman to third overall behind Laurent Pellier, but he delivered a stunning final-day performance to climb back ahead of the Frenchman - turning a 19.7sec deficit into a tiny 0.6sec advantage in second place.
Paraguay's Diego Dominguez was fourth overall, while Tom Rensonnet - making his snow and ice debut - completed the top five.