| Birth Date: | 19 May 1884 |
| Birth Place: | Eslöv, Sweden |
| Death Date: | 20 June 1956 (aged 72) |
| Death Place: | Stockholm, Sweden |
| Sport: | Wrestling |
| Event: | Greco-Roman wrestling |
| Weight Class: | 73 kg |
| Club: | IK Sparta, Malmö |
| Show-Medals: | yes |
Folke Frithiof Martens Mårtensson (19 May 1884 – 20 June 1956) was a Greco-Roman wrestler from Sweden.[1] He won the middleweight contests at the 1908 Summer Olympics in London and at the unofficial 1909 European Championships in Malmö.
After 1909 Mårtensson moved to Copenhagen for training as a dental technician and in 1913 to the United States. Two years later he returned to Stockholm, where he died in 1956.