Ludhiana is a city and a municipal corporation in Ludhiana district in the Indian state of Punjab. It is the largest city in the state, with an estimated population of 1,613,878 in 2011. The population increases substantially during the crop harvesting season due to migration of labourers from states like eastern Uttar Pradesh, Bihar, Odisha and Delhi. It has an area of about 310 km². The city stands on the Sutlej River's old bank, 13 km south of its present course. It is a major industrial centre of northern India. Residents of the city may be referred to as Ludhianvis.
Ludhiana is located 100 km west from state capital Chandigarh on NH 95 and is centrally located on National Highway 1 from Indian capital New Delhi to Amritsar, and is well connected to New Delhi by road, frequent train service and by air.
Ludhiana is a well known NRI district of Punjab with a large population living abroad in Canada, U.K, Australia and U.S.
According to the WHO, Ludhiana is the world's most polluted city