Lodewicus Theodorus "Louis" Oosthuizen (Afrikaans pronunciation: , which he pronounced for the American audience in this TV ad; born 19 October 1982) is a South African professional golfer, who won the 2010 Open Championship.
Oosthuizen was born in Mossel Bay, South Africa. His early career was supported financially for three years by the foundation of fellow South African Ernie Els. He won numerous amateur titles before turning professional in 2002 at the age of 19.
He has won five professional tournaments on the Sunshine Tour: the 2004 Vodacom Origins of Golf Tour event at Arabella, the 2007 Dimension Data Pro-Am and Platinum Classic, and the Telkom PGA Championship twice, in 2007 and 2008. He played on the European Challenge Tour in 2003 and has been a member of the European Tour since 2004. In 2009, he finished 31st on the Race to Dubai. He has featured in the top 50 of the Official World Golf Rankings.