| Birth Date: | 11 January 1904 |
| Birth Place: | Hanover, Northern Cape, South Africa |
| Death Date: | 3 September 1976 (aged 72) |
| Death Place: | Centurion, Gauteng, South Africa |
| Sport: | Athletics |
| Event: | Decathlon |
| Pb: | 100 yd – 9.8 (1929) 110 mH – 14.6y (1933) LJ – 7.50 m (1929) HJ – 1.905 m (1930) |
| Show-Medals: | yes |
Johannes Hendrikus "Snaar" Viljoen (11 January 1904 - 3 September 1976) was a South African athlete. He competed at the 1928 Summer Olympics in the long jump, triple jump, 100 meters, 110 meter hurdles and decathlon, but failed to reach the finals.
At the 1930 Empire Games he won the gold medal in the high jump and the bronze medal in the long jump, finishing fourth in the 120 yards hurdles. He also participated in the 220 yards, in the 440 yards hurdles, and in the hammer throw contests. Four years later at the 1934 British Empire Games he reached the 120 yards hurdles final, but did not finish the race.