Born in Oxfordshire to an aristocratic family, Churchill was a son of Lord Randolph Churchill and Jennie Jerome. Joining the British Army, he saw action in British India, the Anglo–Sudan War, and the Second Boer War, gaining fame as a war correspondent and writing books about his campaigns. Elected an MP in 1900, initially as a Conservative, he defected to the Liberals in 1904. In H. H. Asquith's Liberal government, Churchill served as President of the Board of Trade, Home Secretary, and First Lord of the Admiralty, championing prison reform and workers' social security. During the First World War, he oversaw the Gallipoli Campaign; after it proved a disaster, he resigned from government and served in the Royal Scots Fusiliers on the Western Front. In 1917 he returned to government under David Lloyd George as Minister of Munitions, and was subsequently Secretary of State for War, Secretary of State for Air, then Secretary of State for the Colonies. After two years out of Parliament, he served as Chancellor of the Exchequer in Stanley Baldwin's Conservative government, returning the pound sterling in 1925 to the gold standard at its pre-war parity, a move widely seen as creating deflationary pressure on the UK economy.
Out of office during the 1930s, Churchill took the lead in calling for British rearmament to counter the growing threat from Nazi Germany. At the outbreak of the Second World War, he was re-appointed First Lord of the Admiralty. Following Prime Minister Neville Chamberlain's resignation in 1940, Churchill replaced him. Churchill oversaw British involvement in the Allied war effort, resulting in victory in 1945. His wartime response to the 1943 Bengal famine, which claimed an estimated three million lives, has caused controversy, and he sanctioned the 1945 bombing of Dresden, which caused tens of thousands of civilian deaths and continues to be debated. After the Conservatives' defeat in the 1945 general election, he became Leader of the Opposition. Amid the developing Cold War with the Soviet Union, he publicly warned of an "iron curtain" of Soviet influence in Europe and promoted European unity. He was re-elected prime minister in the 1951 election. His second term was preoccupied with foreign affairs, including the Malayan Emergency, Mau Mau Uprising, Korean War, Syrian crisis and a UK-backed Iranian coup. Domestically his government emphasised house-building and developed an atomic bomb. In declining health, Churchill resigned as prime minister in 1955, although remained an MP until 1964. Upon his death in 1965, he was given a state funeral.
Widely considered one of the 20th century's most significant figures, Churchill remains popular in the UK and Western world, where he is seen as a victorious wartime leader who played an important role in defending liberal democracy from the spread of fascism. Also praised as a social reformer and writer, among his many awards was the Nobel Prize in Literature. Conversely, his imperialist and racist views—coupled with his sanctioning of human rights abuses in the suppression of anti-imperialist movements seeking independence from the British Empire—have generated considerable controversy.
Churchill was born at his parental home, Blenheim Palace in Oxfordshire, on 30 November 1874, at which time the United Kingdom was the dominant world power. A direct descendant of the Dukes of Marlborough, his family were among the highest levels of the British aristocracy, and thus he was born into the country's governing elite. His paternal grandfather, John Spencer-Churchill, 7th Duke of Marlborough, had been a Member of Parliament (MP) for ten years, a member of the Conservative Party who served in the government of Prime Minister Benjamin Disraeli. His own father, Lord Randolph Churchill, had been elected Conservative MP for Woodstock in 1873. His mother, Jennie Churchill (née Jerome), was from an American family whose substantial wealth derived from finance. The couple had met in August 1873, and were engaged three days later, marrying at the British Embassy in Paris in April 1874. The couple lived beyond their income and were frequently in debt; according to the biographer Sebastian Haffner, the family were "rich by normal standards but poor by those of the rich".
In 1876 John Spencer-Churchill was appointed Viceroy of Ireland, with Randolph as his private secretary, resulting in the Churchill family's relocation to Dublin, when the entirety of Ireland was part of the United Kingdom. It was here that Jennie's second son, Jack, was born in 1880; there has been speculation that Randolph was not his biological father. Throughout much of the 1880s Randolph and Jennie were effectively estranged, during which she had many suitors. Churchill had virtually no relationship with his father; referring to his mother, Churchill later stated that "I loved her dearly - but at a distance." His relationship with Jack would be warm, and they were close at various points in their lives. In Dublin, he was educated in reading and mathematics by a governess, while he and his brother were cared for primarily by their nanny, Elizabeth Ann Everest. Churchill was devoted to her and nicknamed her "Woomany"; he later wrote that "She had been my dearest and most intimate friend during the whole of the twenty years I had lived."