Gainsborough is a market town, inland port and civil parish in the West Lindsey district of Lincolnshire, England. The population was 20,842 at the 2011 census, and estimated at 23,243 in 2019. It lies on the east bank of the River Trent, 18 miles (29 km) north-west of Lincoln, 16 miles (26 km) south-west of Scunthorpe, 20 miles south-east of Doncaster and 39 miles (63 km) east of Sheffield. It is England's furthest inland port at over 55 miles (89 km) from the North Sea.

West Lindsey is a local government district in Lincolnshire, England. Its council is based in Gainsborough, the district's largest town. The district also includes the towns of Caistor and Market Rasen, along with numerous villages and surrounding rural areas. The east of the district includes part of the Lincolnshire Wolds, a designated Area of Outstanding Natural Beauty.