A fogou or fougou is an underground, dry-stone structure found on Iron Age or Romano-British-defended settlement sites in Cornwall. The original purpose of a fogou is uncertain today. Colloquially called vugs, vows, foggos, giant holts, or fuggy holes in various dialects, fogous have similarities with souterrains or earth-houses of northern Europe and particularly Scotland, including Orkney. Fewer than 15 confirmed fogous have been found.

Souterrain is a name given by archaeologists to a type of underground structure associated mainly with the European Atlantic Iron Age.