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, increasing to 429 at the 2011 census.