By tournament:

1973 Ford Sevens

The list may be subject to change if more rugby union sevens tournaments are discovered.

Ford Sevens

From The Official History of the Melrose Sevens by Walter Allan:

The first domestic tournament did not take place until the Ford Sevens were held in Pretoria in 1973.

Winfield Sevens

The Winfield Sevens is a national tournament for South African provincial teams.