Already victorious at Oberstdorf and Garmisch in Germany, and then second at Innsbruck on Wednesday, the 26-year-old defeated closest rivals Anze Lanisek of Slovenia and Poland's Dawid Kubacki.
Granerud finished the tournament on a record 1,191.2 points, 33 ahead of Kubacki and 62.2 points in front of Lanisek.
He is the first Norwegian to win the Four Hills since Anders Jacobsen in 2007.