Mulayam Singh Yadav was born to Murti Devi and Sughar Singh on 22 November 1939 in the village Saifai of Etawah district of Uttar Pradesh in India.
He has gained several degrees — a B.A., B.T., and an M.A. in political science — through his education at K.K. College in Etawah, A.K. College in Shikohabad and B.R. College, Agra University.
Yadav married twice. His first wife was Malti Devi, whose son is Akhilesh Yadav (born 1973), the current Chief Minister of Uttar Pradesh. Malti Devi died in May 2003. Yadav's second wife is Sadhna Yadav, with whom he has a son named Prateek Yadav (born 1988) Prateek manages land holdings of the Yadav family. Mulayam's second wife was not well known till February 2007, when he admitted for the first time in India's Supreme Court that he had two wives.

Yadav was first elected as a Member of the Legislative Assembly in Legislative Assembly of Uttar Pradesh in 1967. Yadav served eight terms there. He first became a state minister in 1977. Later, in 1980, he became the president of the Lok Dal (People's Party) in Uttar Pradesh which became a part of the Janata Dal (People's Party) afterward. In 1982, he was elected leader of the opposition in the Uttar Pradesh Legislative Council and held that post until 1985.

First term as chief minister
Yadav first became Chief Minister of Uttar Pradesh in 1989.

After the collapse of the V P Singh government at the centre in November 1990, Yadav joined Chandra Shekhar's Janata Dal (Socialist) party and continued in office as chief minister with the support of the Congress Party. His government fell when the Congress withdrew support to his government in April 1991 in reaction to the aftermath of developments at the centre, wherein the Congress party withdrew support to Chandra Shekhar's government. Mid-term elections to Uttar Pradesh assembly were held in mid-1991, in which Mulayam Singh's party lost power to the BJP.

Second term as chief minister
In 1992, Yadav founded his own Samajwadi Party (Socialist Party). In 1993, he allied with the Bahujan Samaj Party for the elections to Uttar Pradesh assembly due to be held in November 1993. The alliance between Samajwadi Party and Bahujan Samaj Party prevented the return of BJP to power in the state. Though the alliance did not win the majority,[citation needed] Yadav became chief minister of Uttar Pradesh with the support of Congress and Janata Dal. His stand on movement for demanding separate statehood for Uttarakhand was as much controversial as his stand on Ayodhya movement in 1990 was. There was a firing on Uttarakhand activists at Muzaffarnagar on 2 October 1994, something for which Uttarakhand activists held him responsible. He continued holding that post until his ally opted into another alliance in June 1995.
As union cabinet minister
In 1996, Yadav was elected to the eleventh Lok Sabha from Mainpuri constituency. In the United Front coalition government formed that year, his party joined and he was named India's Defence Minister. That government fell in 1998 as India went in for fresh elections, but he returned to the Lok Sabha that year from Sambhal parliamentary constituency. After the fall of Atal Bihari Vajpayee government at the center in April 1999, he did not support the Congress party in the formation of the government at the Centre. He contested Lok Sabha elections of 1999 from two seats, Sambhal and Kannauj, and won from both. He resigned from Kannauj seat for his son Akhilesh in the by-elections.

Third term as chief minister
In 2002, following a fluid post-election situation in Uttar Pradesh, the Bharatiya Janata Party and Bahujan Samaj Party joined to form a government under dalit leader Mayawati, considered to be Mulayam's greatest rival[citation needed]. After a one-and-a-half year stint, the BJP pulled out of the government on 25 August 2003, and enough rebel legislators of the Bahujan Samaj Party left to allow Mulayam to become the Chief Minister, with the support of independents and small parties.[citation needed] Mulayam Singh Yadav was sworn in as chief minister of Uttar Pradesh for the third time in September 2003. It is widely believed that this change was done with the blessings of the BJP, which was also ruling at the Centre then.
In September 2003, when Yadav was sworn in as chief minister of Uttar Pradesh, Yadav was a member of the Lok Sabha. In order to meet the constitutional requirement of becoming the member of state legislature within 6 months of being sworn in, Yadav contested the assembly by-election from Gunnaur assembly seat in January 2004. Yadav won by a record margin and polled almost 92% of the total votes. Yadav's victory margin of 183,899 votes is the highest margin of victory in assembly elections so far.
With the hope of playing a major role at the center, Yadav contested Lok Sabha elections of 2004 from Mainpuri when Yadav was the chief minister of Uttar Pradesh. Yadav won the seat and his party, Samajwadi Party won more seats in Uttar Pradesh than all other parties.[citation needed] However the Congress party, which formed the coalition government at the center after the elections had majority in the Lok Sabha with the support of the communist parties. As a result, Yadav could not play any significant role at the center, Yadav resigned from Lok Sabha and chose to continue as chief minister of Uttar Pradesh until he lost 2007 election when he lost to BSP.