Lodewicus Theodorus "Louis" Oosthuizen (; born 1982) is a South African professional golfer who won the 2010 Open Championship. He has finished runner-up in all four major championships: the 2012 Masters Tournament, the 2015 and 2021 U.S. Open, the 2015 Open Championship, and the PGA Championship in 2017 and 2021. His highest placing on the Official World Golf Ranking is fourth, which he reached in January 2013.