Louis Theodor Weichardt (21 May 1894 – 26 October 1985) was a South African political leader, born in Paarl of German extraction, who founded the Greyshirts, a Nazi organization.

In Cape Town, on 26 October 1933, Weichardt founded the South African Christian National Socialist Spider Movement with a paramilitary section (modeled on Nazi Germany's brown-shirted Sturmabteilung) called the Gryshemde or Grayshirts. He was interned during World War II, and released from custody in 1946. Afterwards, he worked with Oswald Pirow's New Order. Disbanding his party in 1948, Weichardt gave his allegiance to Daniel François Malan's National Party. He became senator from Natal Province from 1956 to 1970.

• Biographical Dictionary of the Extreme Right Since 1890 edited by Philip Rees (1991, ISBN 0-13-089301-3)
• Fascism: Comparison and Definition by Stanley G. Payne (University of Wisconsin–Madison Press, 1980, ISBN 0-299-08060-9)
• The South African Opposition 1939-1945 by Michael Roberts & A.E.G. Trollip (Cape Town, 1947)

• "Vote for Louis Weichardt" on the Simon Wiesenthal Center website
• Louis Weichardt; Greyshirt leader, 1937 newspaper photo on the Simon Wiesenthal Center website