Muzaffarpur () is a city located in Muzaffarpur district in the Tirhut region of the Indian state of Bihar. It serves as the headquarters of the Tirhut division, the Muzaffarpur district and the Muzaffarpur Railway District. It is the fourth most populous city in Bihar.
Muzaffarpur is famous for Shahi lychees and is known as the Lychee Kingdom. Shahi litchi is set to become the fourth product from Bihar, after jardalu mango, katarni rice and Magahi paan (betel leaf) to get the Geographical Indication (GI) tag. It is situated on the banks of the perennial Budhi Gandak River, which flows from the Someshwar Hills of the Himalayas.
The current city was established in 1875 during the British Raj for administrative convenience, by dividing the Tirhut district and was named after an aumil, Muzaffar Khan; thus the city came to be known as Muzaffarpur.
The city was founded by Muẓaffar Khan in the 18th century and was constituted a municipality in 1864. A major road and rail hub, it is a trade centre on the route between Patna (south) and Nepal (north). Lychee, sweet corn, mango, vegetables, rice and sugar milling alongside cutlery manufacturing are the chief industries.
In 1972, the Sitamarhi and Vaishali districts were split off from Muzaffarpur.
Muzaffarpur is located at . The city lies in a highly active seismic zone of India. In the disastrous earthquake on 15 January 1934, much of the town suffered severe damage and many people died. It has an average elevation of 47 meters (154 feet). This saucer shaped, low-centered town lies on the great Indo-Gangetic plains of Bihar, over Himalayan silt and sand brought by the glacier-fed and rain-fed meandering rivers of the Himalayas.
Muzaffarpur has a humid subtropical climate (Cwa) under the Köppen climate classification. The summer, between April and June, is extremely hot and humid (28-40 °C, 90% max). and winter is pleasantly cool, around 06-20 °C. Rainfall in Muzaffarpur City is comparatively less compared to other parts of Bihar.
As of the 2011 India census, Muzaffarpur had a population of 393,724.