| Birth Date: | 13 October 1897 |
| Birth Place: | Fellingsbro, Sweden |
| Death Date: | 15 December 1953 (aged 56) |
| Death Place: | Eskilstuna, Sweden |
| Height: | 1.89m (06.2feet) |
| Weight: | 108kg (238lb) |
| Sport: | Athletics |
| Event: | Hammer throw |
| Club: | IFK Eskilstuna |
| Pb: | 53.41 m (1935) |
| Show-Medals: | yes |
Johan Gunnar Jansson (13 October 1897 – 15 December 1953) was a Swedish hammer thrower who won a bronze medal at the 1934 European Championships. He competed at the 1932 and 1936 Summer Olympics and finished in 7th and 12th place, respectively. Jansson held Swedish titles in the hammer throw in 1931, 1933–35 and 1937 and in the weight throw in 1929–31, 1933–35, 1937 and 1938.