The Diesel Locomotive Works (DLW) in Varanasi, India, is a production unit owned by Indian Railways, that manufactures diesel-electric locomotives and its spare parts. It is the largest diesel-electric locomotive manufacturer in India. It is located on DLW to BHU road of the metropolitan city of Varanasi.

Founded in 1961, the DLW rolled out its first locomotive three years later, on 3 January 1964. It manufactures locomotives which are variants based on the original ALCO designs dating to 1960s and the GM EMD designs of the 1990s. DLW has an annual production capacity of 250 locomotives and plans to increase it to 275 based on the current demand. Since inception, DLW has produced total 8099 locomotives (up to 31 January 2018) of various types. DLW now manufactures "More than one locomotive a day". DLW manufactured 334 diesel-electric locomotives in last financial year 2016-17, which is the highest ever loco production by any loco manufacturing unit in India and bagged the "Best Production Unit Shield" for the second successive year.

DLW locomotives have power outputs ranging from 2,600 horsepower (1,900 kW) to 5,500 horsepower (4,100 kW). Currently DLW is producing EMD GT46MAC and EMD GT46PAC locomotives under license from Electro-Motive Diesels (formerly GM-EMD) for Indian Railways. Some of its EMD locomotive products are WDP4, WDP4D, WDG4D, WDG5 and others as of June 2015. DLW recently started producing HEP capable WAP-7 high horsepower Electric Locomotives. Recently, it has been allotted to Santragachi & Tughlakabad Loco Shed.[5] It will also produce WDG4G (ES43ACmi, Customized for IR) Locomotives From General-Electric Transportation.

Besides the Indian Railways, it regularly exports diesel-electric locomotives and has supplied locomotives to other countries such as Sri Lanka, Nepal, Bangladesh, Mali, Senegal, Sudan Tanzania, Angola, and Vietnam and also to a few users within India, such as ports, large power and steel plants and private railways.

In July 2006, DLW outsourced manufacture of some passenger and freight locomotives to Parel Workshop, Central Railway, Mumbai.