The prime minister of India (ISO: Bhārat kē Pradhānamantrī) is the head of government of the Republic of India. Executive authority is vested in the prime minister and his chosen Council of Ministers, despite the president of India being the nominal head of the executive. The prime minister has to be a member of one of the houses of bicameral Parliament of India, alongside heading the respective house. The prime minister and the cabinet are at all times responsible to the Lok Sabha.

The sitting prime minister ranks third in the Order of Precedence of India and is appointed by the president of India; however, the prime minister has to enjoy the confidence of the majority of Lok Sabha members, who are directly elected every five years, lest the prime minister shall resign. The prime minister can be a member of the Lok Sabha or the Rajya Sabha, the upper house of the parliament. The prime minister controls the selection and dismissal of members of the Union Council of Ministers and allocation of posts to members within the government.

The longest-serving prime minister was the first prime minister, Jawaharlal Nehru, whose tenure lasted 16 years and 286 days. His premiership was followed by Lal Bahadur Shastri's short tenure and Indira Gandhi's 11- and 4-year-long tenures, with both politicians belonging to the Indian National Congress. After Indira Gandhi's assassination, her son Rajiv Gandhi took charge until 1989, when a decade with five unstable governments began. This was followed by the full terms of P. V. Narasimha Rao, Atal Bihari Vajpayee, Manmohan Singh, and Narendra Modi, who is the current prime minister of India, serving since 26 May 2014. He is the first non-Congress leader to win three consecutive general elections and secure a third successive term (2014, 2019, 2024). The first prime minister to do so was Jawaharlal Nehru, who won the general elections of 1952, 1957, and 1962.

India follows a parliamentary system in which the prime minister is the presiding head of the government and chief of the executive of the government. In such systems, the head of state, or, the head of state's official representative (i.e., the monarch, president, or governor-general) usually holds a purely ceremonial position and acts, on most matters, only on the advice of the prime minister.

The prime minister must become a member of parliament within six months of beginning their tenure, if they are not one already. A prime minister is expected to work with other central ministers to ensure the passage of bills by the parliament.

Since 1947, there have been 14 different prime ministers. The first few decades after 1947 saw the Indian National Congress' (INC) near complete domination over the political map of India. India's first prime minister, Jawaharlal Nehru, took oath on 15 August 1947. Nehru went on to serve as prime minister for 17 consecutive years, winning four general elections in the process. His tenure ended in May 1964, on his death. After the death of Nehru, Lal Bahadur Shastri, a former home minister and a leader of the Congress party, ascended to the position of prime minister. Shastri's tenure saw the Indo-Pakistani War of 1965. Shashtri subsequently died of a reported heart attack in Tashkent, after signing the Tashkent Declaration.

After Shastri, Indira Gandhi, Nehru's daughter, was elected as the country's third prime minister. The first, and to date, the only, woman to hold the post, Indira's first term in office lasted 11 years, in which she took steps such as nationalisation of banks; end of allowances and political posts, which were received by members of the royal families of the erstwhile princely states of the British Indian Empire. In addition, events such as the Indo-Pakistani War of 1971; the establishment of a sovereign Bangladesh; accession of Sikkim to India, through a referendum in 1975; and India's first nuclear test in Pokhran occurred during Indira's first term. In 1975, amid growing unrest and a court order declaring Indira's election to the Lok Sabha void, President Fakhruddin Ali Ahmed, on Indira's advice, imposed a state of emergency, therefore bestowing the government with the power to rule by decree; this period is known for human rights violations such as mass sterilisation and the imprisonment of Indira's political opponents.

After widespread protests, the emergency was lifted in 1977, and a general election was held. All of the political parties of the opposition, after the conclusion of the emergency, fought together against the Congress, under the umbrella of the Janata Party, in the general election of 1977, and were successful in defeating the Congress. Subsequently, Morarji Desai, a former deputy prime minister, became the first non-Congress prime minister of India. Desai's government was composed of groups with opposite ideologies, in which unity and coordination were difficult to maintain. Ultimately, after two and a half years as PM; on 28 July 1979, Desai tendered his resignation to the president; and his government fell. Thereafter, Charan Singh, a deputy prime minister in Desai's cabinet, with outside, conditional support from Congress, proved a majority in Lok Sabha and took oath as Prime Minister. However, Congress pulled its support shortly after, and Singh had to resign; he had a tenure of 5 months, the shortest in the history of the office.