| Birth Date: | 8 September 1893 |
| Birth Place: | Länna, Uppsala Municipality, Sweden |
| Death Date: | 15 January 1977 (aged 83) |
| Death Place: | Sundbyberg, Stockholm, Sweden |
| Height: | 1.69m (05.54feet) |
| Weight: | 60kg (130lb) |
| Sport: | Athletics |
| Event: | 3,000 m – marathon |
| Club: | Fredrikshofs IF, Stockholm |
| Pb: | 3000 mS – 10:05.4 (1923) 5000 m – 15:18.7 (1921) 10,000 m – 32:04.2 (1921)[1] |
| Show-Medals: | yes |
Gustaf Isidor Mattsson (8 September 1893 – 15 January 1977) was a Swedish long-distance runner.[2] He competed at the 1920 Summer Olympics in the 3,000 m steeplechase and 8,000 m cross-country events and finished in fourth and tenth place, respectively. His tenth place earned him a bronze medal with the Swedish team.[3]
Mattsson competed over distances ranging from 3,000 m to marathon and won three Swedish titles over 20 km on the road. He was a businessman by trade.