Grantham is a market town within the South Kesteven district of Lincolnshire, England.

Grantham is located approximately 26 miles (42 km) south of the city of Lincoln, and approximately 24 miles (39 km) east of Nottingham.

With the housing estates in Londonthorpe and Harrowby Without (around a population of 4,500), this figure would be around 42,000.

Grantham is within short walking distance of an ancient Roman road, and was the scene of Oliver Cromwell's first advantage over Royalists during the English Civil War at Gonerby Moor.

Grantham produced the first running diesel engine in 1892, and the UK's first tractor in 1896.

It bestrides the East Coast Main Line railway (London-Edinburgh), the historic A1 main north-south road, and the River Witham.

Its population at the 2001 census was 34,592 with around 18,000 households, excluding the adjacent village of Great Gonerby.

It is best known as the birthplace of former prime minister Margaret Thatcher, and the place where Isaac Newton went to school.

It is also notable for having the first female police officers in the United Kingdom, in 1914.

Its town boundary crosses the A1 to the west at the Dysart Road bridge.