Lodewikus Theodorus "Theo" Oosthuizen (born 24 February 1964) is a former rugby union player who represented both South Africa and Namibia.
Oosthuizen made his debut for South West Africa in 1988 and after independence of Namibia in 1990, he played in Namibia's first test match on 24 March 1990 in Windhoek against Zimbabwe.
In total, Oosthuizen played seven test matches for Namibia, scoring two tries.
[3][4] In 1992 he returned to the Free State and in 1994 relocated to play for Griqualand West (now known as Griquas) at provincial level.
[5] There was talk that he was included in the 1996 South African touring team to Argentina and Europe on the basis of his friendship with then coach Andre Markgraaff, who was also involved with that particular provincial side.