The Bihar Legislative Assembly election was held in three phases through October–November to elect members to the Seventeenth Bihar Legislative Assembly. The term of the previous Sixteenth Legislative Assembly of Bihar ended on 29 November 2020.

The election was held in three phases for a total of 243 seats:- the first for 71 seats on 28 October 2020, the second for 94 seats on 3 November 2020, and the third for the remaining 78 seats on 7 November 2020. The counting of votes began on 10 November 2020 and the incumbent National Democratic Alliance emerged as the winner with 125 elected MLAs, whereas the principal opposition coalition of Mahagathbandhan won 110 seats. Other minor coalitions and parties won 7 seats while only 1 newly elected MLA was an independent.

After the elections, the incumbent Chief Minister Nitish Kumar was elected as the leader of the National Democratic Alliance in Bihar and was sworn in again as Chief Minister, whereas two new deputy Chief Ministers, Tarkishore Prasad and Renu Devi were inducted to the new ministry. On the other side, Tejashwi Yadav was elected Leader of the Opposition, and also leader of the Mahagathbandhan alliance. Later Vijay Kumar Sinha was elected the new Speaker of the Bihar Legislative Assembly.

Outlined in Article 168 of the Constitution of India, the Bihar Legislative Assembly is the lower house of the bicameral legislature of Bihar and not a permanent body and subject to dissolution. The tenure of the Legislative Assembly is five years from the date appointed for its first sitting unless dissolved sooner. Members of the Legislative Assembly are directly elected by the people. The Tenure of current Bihar Legislative Assembly is scheduled to end on 29 November 2020.

In the previous election, an alliance of three Major Parties consisting of Janata Dal (United), Rashtriya Janata Dal and Indian National Congress named as Mahagathbandhan won against its primary opposition, the Bharatiya Janata Party led National Democratic Alliance. However, in 2017, the Janata Dal (United) Chief Minister Nitish Kumar left the Mahagathbandhan and joined the National Democratic Alliance. While Nitish Kumar remained the Chief Minister, Sushil Kumar Modi of the Bharatiya Janata Party replaced Tejashwi Yadav as the Deputy Chief Minister.

The main issue was that of the jobs and the economy. Bihar, for a long time, has been an economically backward state and sends large numbers of migrant laborers to cities across the country. Due to the coronavirus pandemic lockdown, thousands of migrant laborers were forced to return to their home states due to lack of work, and Bihar was one of the most affected by the ensuing humanitarian crisis. Many of these workers blamed the current government for not having jobs for them in the first place, and not providing jobs when the lockdown started. There was also a significant anti-incumbency wave against Nitish, who had been CM for 15 years.

The three agriculture bills passed by the Indian Parliament amid nationwide protests was expected to play a key role in the elections.

Issues such as the lack of employment, alleged politicisation of flood relief in the aftermath of the 2019 Bihar floods and alleged inability of the state government to handle the COVID-19 pandemic were expected to be made an election issue by the opposition parties. The limited digital connectivity in Bihar and the migrant crisis were among the issues which may have had an impact on campaigning and poll outcomes.