Narendra Modi, leader of the Hindu Nationalist Bharatiya Janata Party (BJP), has taken oath as India's prime minister for a third time.
The ceremony took place at Rashtrapati Bhavan, the official residence of the Indian president.
Mr Modi's BJP-led National Democratic Alliance won the general election with 293 seats, a lower margin than predicted by exit polls.
The election saw a resurgence of India's opposition, which won 234 seats.
Thousands of guests have been attending his inauguration at Delhi's Presidential Palace. Among them are the heads of neighbouring Bangladesh, Nepal, Sri Lanka, and the Maldives.
Tight security has been in place in Delhi, which was declared a no-fly zone, with more than 2,500 police officers deployed around the venue.
During the ceremony, President Draupadi Murmu has also been swearing in a council of ministers of Mr Modi's new cabinet.
Exit polls had projected outright victory for his BJP party which ruled India for a decade, but it lost its parliamentary majority in the election.
His NDA bloc relied on two key allies, the Telugu Desam Party (TDP) and the Janata Dal (United) JD(U), to cross the 272-seat mark needed to form the government.
On Friday, the elected MPs voted Mr Modi as the leader of the Lok Sabha (the lower house of the parliament), leader of the BJP parliamentary party, and leader of the NDA.
It is not clear what concessions his allies may have negotiated in return for their support. India media report that several are seeking key ministerial posts.
The opposition INDIA alliance, led by the Congress party, has called the election a mandate against Mr Modi's government.
Mr Modi, however, countered this on Friday, saying: "Opposition tried to paint 2024 Lok Sabha results as a loss for us. But we didn’t lose, we never lost, we will never lose."
Mr Modi thanked voters for their mandate, and said he would "do everything" to eradicate corruption and poverty.
"Empowering the poor and middle class is our priority," he said.
During his election campaign, Mr Modi and his party were accused by critics of using hate speech, attacking the country's Muslim minority, and jailing opposition figures.
On Friday, the prime minister-elect said the NDA alliance was "committed to the principle of "sarva panth sambhava" (religious equality).
The INDIA alliance has said it will fulfil its duty in parliament by holding the government in check and protecting the constitution.
