George Henry Lane-Fox Pitt-Rivers (22 May 1890 – 17 June 1966) was a British anthropologist and eugenicist who was a wealthy landowner in England in the interwar period. He embraced anti-Bolshevism and anti-Semitism and became a supporter of Oswald Mosley, which led to him being interned by the British government in the Second World War.

Pitt-Rivers was born in London, his birth registered under the surname Fox in Chesterfield. He was a son of Alexander Edward Lane Fox-Pitt-Rivers (2 November 1855 – 19 August 1927) and his wife Alice Ruth Hermione, daughter of Lord Henry Thynne. His father was the eldest son of Augustus Pitt Rivers, ethnologist and anthropologist and founder of the Pitt Rivers Museum, upon whose death in 1900 Alexander inherited the Pitt-Rivers estate. After Alexander died in 1927, the estate was inherited by George and it was so large that "it was said, albeit with exaggeration, that he could ride from coast to coast without leaving his own land".

Pitt-Rivers was an officer in the 1st (Royal) Dragoons. In November 1911, his regiment was sent to South Africa, being stationed in Johannesburg, the centre of the gold-mining industry of the Witwatersrand. In June 1913, the gold miners went on strike, demanding fewer hours and more pay. General Jan Smuts, the South African minister of defence and of finance, decided to use military force to end the strike, and on 4 July 1913 the Dragoons were ordered to break up a pro-strike rally in Market Square, Johannesburg, leading to a bout of extended fighting and rioting that lasted until the following day. Pitt-Rivers' precise role in the action in Johannesburg remains unclear, though as a junior officer he was certainly involved. In the aftermath, he took photographs of the burned-out buildings and the horses of the Dragoon Guards that had been killed during the shooting. The action in Johannesburg left him with a strong dislike of unions and the political left in general.

He took part in the First World War. On 23 August 1914, the Dragoons left South Africa for England and on 7 October 1914 arrived in Belgium. In October and November, the Dragoon Guards were involved in heavy fighting during the First Battle of Ypres. On 17 November 1914, Pitt-Rivers's knee was shattered by a German bullet, and he was sent to England for surgery and recuperation. He was promoted to captain in 1919.

With the ending of the war, Pitt-Rivers was in an insecure mood as he noted that the world that existed before 1914 would not return, and that the United Kingdom was entering a new age. In 1920 he published a book, with a preface by Oscar Levy, The World Significance of the Russian Revolution, the first of his anti-Bolshevik and anti-Semitic public activities. In it he wrote "the Jews are the principal agents of economic and political misery in the world, through their dealings in international finance and their actions in promoting democracy and revolution".

From 1922 to 1925, Pitt-Rivers held the position of Principal Secretary and Aide-de-Camp to his father-in-law Lord Forster, the Governor-General of Australia. He disliked Australia, which he found too democratic for his tastes, and spent as much time as possible out of the country on field research in New Zealand, New Guinea, the Bismarck Archipelago and elsewhere in the South Pacific. The focus on his anthropology studies in the Pacific was on "race extinction", "sex-ratio variances" and "culture extinction". His experience with the Māori people led to his lasting interest in anthropology, which he studied at Oxford under Bronisław Malinowski. Pitt-Rivers was described by the British historian Richard Griffins as being "obsessed" with racial questions which he believed to be the prime moving force in human history. In his entry in Who's Who, Pitt-Rivers described himself as having "established the methodology of the science of ethnogenics, interaction of race, population and culture". Influenced by scientific racism, Pitt-Rivers believed that Britain's principal problem was that people with, as he saw it, 'inferior' genes were having too many children, while the people with the "superior" genes were not. Alongside this belief was a vehement opposition to immigration as he believed that immigrants had inferior genes.

In 1927 he attended the World Population Conference and published a book Clash of Cultures and the Contact of Races. Two years later, Pitt-Rivers was elected a fellow of the Royal Anthropological Institute; he also represented the Eugenics Society at the International Federation of Eugenics Organizations. Within the Eugenics Society there was major debate between the followers of Marie Stopes who demanded unlimited birth control and an emphasis on female sexual pleasure for middle-class women, vs. those who found her approach too radical and likely to offend British public opinion. Pitt-Rivers backed the Stopes position of unlimited birth control as he shared her view that British working-class women should be encouraged to use birth control as a way to prevent them from passing on their presumably inferior genes to the next generation. In this way, Pitt-Rivers became estranged from the leaders of the Eugenics Society, who found his views too radical. In 1931, he published Weeds in the Garden of Marriage: The Ethics of Race and Our Captious Critics that attacked the institution of marriage in modern Britain from an euthenic perspective. From 1931 to 1937, Pitt-Rivers held the positions of Secretary General and Treasurer of the International Union for the Scientific Investigation of Population Problems, where he came into contact with German eugenicists Eugen Fischer and his assistant Lothar Loeffler. During this time, he also became involved in politics, praising the ideas of Benito Mussolini and Adolf Hitler. In the 1935 United Kingdom general election, he stood in North Dorset as an "Independent Agriculturist" with backing from the British Union of Fascists. Oswald Mosley and William Joyce spoke at rallies for him during the election.

An anti-Semitic conspiracy theorist, Pitt-Rivers was hostile towards Czechoslovakia, a state that he believed to have been founded as a result of a Jewish-Masonic conspiracy. In 1936, his visit to the Sudetenland was cut short when he was expelled from Czechoslovakia as a "trouble-maker". After his expulsion, Pitt-Rivers told the British press that he had been in the Sudetenland "working for Hitler". Likewise, Pitt-Rivers blamed the Spanish Civil War on "international Jewry". Pitt-Rivers was enraged by the abdication crisis of 1936 and supported the right of King Edward VIII to retain the throne and marry Mrs Wallis Simpson. On 25 December 1936, he wrote to the War Office saying he wanted to his name removed from the list of Army Reserve officers because he "was not prepared to serve in any capacity a Parliamentary despotism, now styled His Majesty's Government". In September 1937, he attended the Nazi Party rally at Nuremberg where he expressed "rabid anti-British views, preferably to German audiences". After his return to England, he always wore a golden swastika badge and claimed to be a close personal friend of Hitler. At the Authors' Club in London, he left around translations of Nazi propaganda into English. He visited Belgium to meet Léon Degrelle of the Rexist Party, and Spain to proclaim his support for the Nationalists in the Spanish Civil War.