Sanquhar is a town in the south of Scotland in Dumfries and Galloway, on the River Nith. It lies north of Thornhill and west of Moffat. It is a Royal Burgh.

Sanquhar is notable for its tiny post office, claimed to be the oldest post office in the United Kingdom. It was also the place where the Covenanters, who opposed episcopalisation of the church, signed the Sanquhar Declaration renouncing their allegiance to the King, an event commemorated by a monument in the main street. The church of St. Brides contains a memorial to James Crichton 'The Admirable Crichton', a sixteenth century polymath. The ruins of Sanquhar Castle stand nearby.

In the arts, the Sanquhar Pantomime Group annually performs a traditional Christmas Pantomime in aid of local charities.

The two main industries were knitting and mining, and there are a number of traditional Sanquhar knitting patterns. The 18th century tollbooth, now the Sanquhar Tolbooth Museum, tells the story of these, and of Sanquar's literary tradition.