| Jack Oosterlaak | |
| Birth Date: | 15 January 1896 |
| Birth Place: | Wellington, Western Cape, South Africa |
| Death Date: | 5 June 1968 (aged 72) |
| Death Place: | Pretoria, Gauteng, South Africa |
| Sport: | Athletics |
| Event: | Sprints |
| Show-Medals: | yes |
Justus Kinloch Ayres Oosterlaak also known as Jack Oosterlaak (15 January 1896 – 5 June 1968), was a South African athlete who competed in the 1920 Summer Olympics.[1]
Oosterlaak finished third behind Harry Edward in the 100 yards event at the British 1920 AAA Championships.[2] [3] [4]
The following month at the 1920 Olympic Games held in Antwerp, Belgium, he competed in the 4 x 400-metre relay where he won the silver medal with his teammates Harry Davel, Clarence Oldfield and Bevil Rudd.[5]