Sivert John Mattsson (born July 18, 1935) is a former Swedish cross-country skier.
Mattsson represented Sweden in international cross-country skiing competitions during the 1950s. His career highlights include competing at the 1952 Winter Olympics in Oslo, Norway, where he placed 14th in the 50 km event. He achieved significant success at the 1954 FIS Nordic World Ski Championships held in Falun, Sweden, where he was a member of the Swedish 4 × 10 km relay team that secured a silver medal.
Mattsson was primarily known for his participation in long-distance cross-country skiing disciplines. He competed during an era when Nordic skiing was a highly prominent sport in Sweden and other Scandinavian countries.
- Cross-country skiing
- Sweden at the 1952 Winter Olympics
- FIS Nordic World Ski Championships