The town is mentioned in the Domesday Book of 1089 as Tresche, derived from Tre Isck, or Town by the Brook. Thirsk is built around a large medieval market square, which still hosts an open-air market each Monday and Saturday. Thirsk posesses a museum and the 15th century church of St Marys.

Thirsk's chief modern claim to fame is that it is the thinly-disguised Darrowby of the late James Herriot's autobiographical books. The home and veterinary surgery of James Herriot, the setting for All Creatures Great and Small and other volumes, have been preserved as a themed museum in the centre of town.