David Ernest Duke (born July 1, 1950) is an American politician, neo-Nazi, conspiracy theorist, and former grand wizard of the Knights of the Ku Klux Klan. From 1989 to 1992, he was a member of the Louisiana House of Representatives for the Republican Party. His politics and writings are largely devoted to promoting conspiracy theories about Jews, such as Holocaust denial and Jewish control of academia, the press, and the financial system. In 2013, the Anti-Defamation League called Duke "perhaps America's most well-known racist and anti-Semite".

Duke unsuccessfully ran as a Democratic candidate for state legislature during the 1970s and 1980s, culminating in his campaign for the 1988 Democratic presidential nomination. After failing to gain any traction within the Democratic Party, he gained the presidential nomination of the minor Populist Party. In December 1988, he became a Republican and claimed to have become a born-again Christian, nominally renouncing antisemitism and racism. He soon won his only elected office, a seat in the Louisiana House of Representatives. He then ran unsuccessful but competitive campaigns for several more offices, including United States Senate in 1990 and governor of Louisiana in 1991. His campaigns were denounced by national and state Republican leaders, including President George H. W. Bush. He mounted a minor challenge to President Bush in 1992.

By the late 1990s, Duke had abandoned his pretense of rejecting racism and antisemitism, and began to openly promote racist and neo-Nazi viewpoints. He then began to devote himself to writing about his political views, both in newsletters and later on the Internet. In his writings, he denigrates African Americans and other ethnic minorities, and promotes conspiracy theories about a Jewish plot to control America and the world. He continued to run for public office through 2016, but after his reversion to open neo-Nazism, his candidacies were not competitive.

During the 1990s, Duke defrauded his political supporters by pretending to be in dire financial straits and soliciting money for basic necessities. At the time, he was in fact financially secure and used the money for recreational gambling. In December 2002, Duke pleaded guilty to felony fraud and subsequently served a 15-month sentence at Federal Correctional Institution, Big Spring in Texas.