Diggins finished sixth in the five-mile Holmenkollen on Saturday, while second overall Moa Ilar finished in 19th place.
There are three competitions left in the World Cup, but Diggins has a lead over Ilar that Ilar cannot catch up with.
This is the fourth time Diggins has won the overall World Cup - the 2020-2021, 2023-2024, 2024-2025 and now 2025-2026 seasons.
The three remaining World Cup races will be held in Lake Placid in the United States, meaning Diggins has competed for the last time on European soil. Next weekend she will finish her career on home soil with a sprint, 10 kilometers classic and 20 kilometers freestyle.
