Thornhill, is a village in Dewsbury, Kirklees, West Yorkshire, England. Historically part of the West Riding of Yorkshire, Thornhill was absorbed into Dewsbury County Borough in 1910. It is located on a hill on the south side of the River Calder, and has extensive views of Dewsbury, Ossett and Wakefield. It is known for its collection of Anglo-Saxon crosses.
Thornhill is mentioned in the Domesday Book of 1086, but Anglo-Saxon crosses and other remains indicate that there was a settlement here by the 9th century. In 1320 Edward II granted a charter for a market and a fair.
In the reign of Henry III Thornhill Hall was the seat of the Thornhill family, who intermarried with the De Fixbys and Babthorpes in the reigns of Edward I and Edward II. In the reign of Edward III, Elizabeth Thornhill, the only child of Simon Thornhill, married Sir Henry Savile. This extinguished the family line of Thornhills of Thornhill which now passed down the Savile line. Thornhill now became the seat of the powerful Savile family. 
The Saviles remained here until the English Civil War when the house was besieged, (having been previously fortified by Sir William Savile, the third baronet of the family), taken and demolished by the forces of Parliament. Some ruins of the house and the moat still remain at Thornhill Rectory Park. This large house had a secret underground passage, that lead to Thornhill Parish Church.  just a few hundred yards away from the park. The passage remained until the early 1990s when it was filled in due to safety reasons.
Monuments to members of the Thornhill and Savile families are in Thornhill Parish Church. 
Thornhill has close ties to coal-mining. In 1893 a mining disaster at Combs Pit killed 139 coal miners. Thornhill Colliery resulted from the merging of Inghams and Combs Collieries in 1948 but closed in 1971.