| Otto Osen | |
| Nationality: | Norwegian |
| Sport: | Long-distance running |
| Event: | Marathon |
| Birth Date: | 4 July 1882 |
| Birth Place: | Roan, Norway |
| Death Place: | Trondheim, Norway |
Otto Osen (4 July 1882 - 3 November 1950) was a Norwegian long-distance runner. He was born in Roan, but represented the club SK Brage in Trondheim.[1] He finished 34th in the marathon at the 1912 Summer Olympics. His personal best time was 2:59.25 hours, achieved in 1912.[2]