Gustaf Isidor Mattsson (8 September 1893 – 15 January 1977) was a Swedish long-distance runner. 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.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.