Yadav, who entered politics when he was 20, was a three-term chief minister of Uttar Pradesh state and a former federal defense minister.
Mulayam Singh Yadav, a veteran Indian politician and three-time chief minister of the country’s most populous state, died after more than six weeks in hospital, his son said.
Yadav, who was 82 years old, entered politics at 20 and became prime minister of the northern state of Uttar Pradesh in 1989.
The state sends the largest number of legislators to the lower house of parliament and a strong showing in Uttar Pradesh is essential for any party or coalition to win power at the federal level.
Affectionately called “Netaji,” or respected leader, by his followers, Yadav became Uttar Pradesh’s prime minister for the second time in 1993, a year after a right-wing Hindu mob demolished the 16th-century Babri Mosque in the city of Ayodhya, unleashing nationwide violence.
He and his Samajwadi Party emerged as defenders of Muslims, who make up a sizable minority in Uttar Pradesh.
Yadav also served as India’s federal defense minister in a coalition government between 1996 and 1998. He was chief minister of Uttar Pradesh for a third time between 2003 and 2007.
In recent years, he handed over the leadership of the party to his son, Akhilesh Yadav, although he remained a senior leader and member of the national parliament.
“My respected father and his ‘Netaji’ are no more,” Akhilesh Yadav said in a tweet from the official Samajwadi Party account on Monday.
The Samajwadi Party, which last held power in the state between 2012 and 2017 with Akhilesh Yadav as prime minister, has come under pressure from India’s ruling Bharatiya Janata Party, which has swept two consecutive state elections since then.
“With Mulayam leaving there will be a vacuum and keeping the party and family together will be a difficult task for his son,” Rajani Ranjan Jha, a former professor and head of the political science department at Benaras Hindu University, told Reuters.