Tattershall Castle is a castle in Tattershall, Lincolnshire, England, about 12 miles (19 km) north east of Sleaford. It is in the care of the National Trust.

Tattershall Castle has its origins in either a stone castle or a fortified manor house, built by Robert de Tattershall in 1231. This was largely rebuilt in brick, and greatly expanded, by Ralph, 3rd Lord Cromwell, Treasurer of England, between 1430 and 1450.

Brick castles are less common in England than stone or earth and timber constructions; when brick was chosen as a building material it was often for its aesthetic appeal or because it was fashionable. The trend for using bricks was introduced by Flemish weavers. There was plenty of stone available nearby, but Cromwell chose to use brick. About 700,000 bricks were used to build the castle, which has been described as "the finest piece of medieval brick-work in England".