Lostwithiel is a civil parish and small town in Cornwall, England at the head of the estuary of the River Fowey, positioned between the A390 road from Tavistock to Truro and the upper tidal reaches of the river. According to the 2001 census it had a population of 2,739. The name Lostwithiel comes from the Cornish "lostwydhyel" which means "tail of a wooded area".
Lostwithiel is a historic borough. The Lostwithiel constituency elected two members to the unreformed House of Commons, but was disenfranchised by the Reform Act 1832. Prior to 1835 it was an "ancient borough" in Powder Hundred. It was made a municipal borough in 1835 and remained as such until 1968, when it became a civil parish within St. Austell Rural District. The town contains the suburbs of Bridgend to the east and Rosehill and Victoria to the west of the River Fowey.