St Martin-by-Looe (Cornish: Penndrumm) is a coastal civil parish in south Cornwall, England, United Kingdom. The parish is immediately east of the town and parish of Looe, seven miles (11 km) south of Liskeard. The parish is in the Liskeard Registration District and the population in the 2001 census was 321.
To the north, the parish is bordered by Morval parish, to the east by Deviock parish, to the west by Looe parish and to the south by the sea. Until 1845 the parish included also East Looe.
The parish church of St Martin of Tours stands outside the civil parish in the hamlet of St Martin at OS Grid Ref SXSX259550 about a mile north of Looe town centre. Thomas Bond, the topographer is buried in the churchyard.
Jonathan Toup, classical scholar, was presented on 28 July 1750 to the rectory of St Martin and held it until his death in 1785.