Lodewicus Theodorus “Louis” Oosthuizen (born 19 October 1982) is a South African golfer.

Oosthuizen was born in Mossel Bay, South Africa. In 2000 he was a member of the South African team that won the World Amateur Team Championships. He won numerous amateur titles before turning professional in 2002 at the age of 19.

He has won three professional tournaments on the Sunshine Tour, the 2004 Vodacom Origins of Golf at Arabella, the 2007 Dimension Data Pro-Am and Telkom PGA Championship. He played on the European Challenge Tour in 2003 and has been a member of the European Tour from 2004 through to 2007.

Amateur wins (6)
2000 World Junior Championship
2001 All African Games (Kenya), Transvaal Amateur Stroke Play Championship (South Africa)
2002 Indian Amateur Open Championship (tied), Irish Amateur Open Stroke Play Championship, Natal Open Stroke Play Championship (South Africa)

Professional wins (3)

Sunshine Tour wins (3)
2004 Vodacom Origins of Golf at Arabella
2007 Dimension Data Pro-Am, Telkom PGA Championship

Team appearances

Amateur
Eisenhower Trophy (representing South Africa): 2002