Indira Priyadarshini Gandhi (Hindi: [ˈɪnd̪ɪɾɑː ˈɡɑːnd̪ʰi] (listen); née Nehru; 19 November 1917 – 31 October 1984) was an Indian politician and stateswoman who served as the third prime minister of India from 1966 to 1977 and from 1980 until her assassination in 1984. She was India's first and, to date, only female prime minister and a central figure of the Indian National Congress. Gandhi was the daughter of Jawaharlal Nehru, the first prime minister of India, and the mother of Rajiv Gandhi, who succeeded her in office as the country's sixth prime minister. Furthermore, Gandhi's cumulative tenure of 15 years and 350 days makes her the second-longest-serving Indian prime minister after her father.

During Nehru's premiership from 1947 to 1964, Gandhi served as his hostess and accompanied him on his numerous foreign trips. In 1959, she played a part in the dissolution of the Communist-led Kerala state government as then-president of the Indian National Congress, otherwise a ceremonial position to which she was elected earlier that year. Lal Bahadur Shastri, who had succeeded Nehru as prime minister upon his death in 1964, appointed her minister of information and broadcasting in his government; the same year she was elected to the Rajya Sabha, the upper house of the Indian Parliament. On Shastri's sudden death in January 1966, Gandhi defeated her rival, Morarji Desai, in the Congress Party's parliamentary leadership election to become leader and also succeeded Shastri as prime minister. She led the Congress to victory in two subsequent elections, starting with the 1967 general election, in which she was first elected to the lower house of the Indian parliament, the Lok Sabha. In 1971, the Congress Party headed by Gandhi managed to secure its first landslide victory since her father's sweep in 1962, focusing on issues such as poverty. Following the 1977 general election, Gandhi was ousted from office and even lost her seat in parliament. Nevertheless, her faction of the Congress Party won the next general election by a landslide, thanks in part to Gandhi's charismatic leadership in opposition to Janata Party rule, the first non-Congress government in independent modern India's history.

As prime minister, Gandhi was known for her political intransigence and unprecedented centralization of power. In 1967, she headed a military conflict with China in which India successfully repelled Chinese incursions in the Himalayas. In 1971, she went to war with Pakistan in support of the independence movement and war of independence in East Pakistan, which resulted in an Indian victory and the creation of Bangladesh, as well as increasing India's influence to the point where it became the sole regional power in South Asia. Gandhi's rule saw India grow closer to the Soviet Union by signing a friendship treaty in 1971, with India receiving military, financial, and diplomatic support from the Soviet Union during its conflict with Pakistan in the same year. Despite India being at the forefront of the non-aligned movement, Gandhi led India to become one of the Soviet Union's closest allies in Asia, with India and the Soviet Union often supporting each other in proxy wars and at the United Nations. Citing separatist tendencies and in response to a call for revolution, Gandhi instituted a state of emergency from 1975 to 1977, during which basic civil liberties were suspended and the press was censored. Widespread atrocities were carried out during that period. Gandhi faced the growing Sikh separatism throughout her second premiership; in response, she ordered Operation Blue Star, which involved military action in the Golden Temple and resulted in bloodshed with hundreds of Sikhs killed. On 31 October 1984, Gandhi was assassinated by her own bodyguards, both of whom were Sikh nationalists seeking retribution for the events at the temple.

Indira Gandhi remains a controversial figure in India, with supporters citing her leadership during victories over geopolitical rivals China and Pakistan, the Green Revolution, a growing economy in the early 1980s, and her anti-poverty campaign that led her to be known as "Mother Indira" (a pun on Mother India) among the country's poor and rural classes. However, critics note her authoritarian rule of India during the Emergency and major atrocities carried out during Operation Blue Star and the Punjab Insurgency. Indira Gandhi still remains one of India's greatest prime ministers, according to polls and public opinion. In 1999, Gandhi was named "Woman of the Millennium" in an online poll organized by the BBC. In 2020, Gandhi was named by Time magazine among the 100 women who defined the past century as counterparts to the magazine's previous choices for Man of the Year.