The term, loosely translated as "cooking place of the deer" or sometimes "wild deer roast", refers to a type of prehistoric cooking site typically identified by a horseshoe-shaped or kidney-shaped mound of fire-cracked stone and charcoal. One such site sits at Ballyconneely in County Clare, a quiet addition to a tradition that stretches back to the Bronze Age.

The standard interpretation of fulachta fia holds that they functioned as outdoor cooking facilities, probably between 1500 and 500 BC, though some examples are older. The process involved heating stones in a fire and then dropping them into a water-filled trough, usually timber-lined, to bring the water to a boil. Repeated heating and plunging eventually shattered the stones, and the accumulated debris formed the distinctive mounds that survive today. More recent scholarship has suggested alternative uses, including textile processing, bathing, or even brewing, and no single explanation has fully settled the debate. The sites are almost always found near a water source, often in low-lying or marshy ground, which suits both the practical requirements of the process and the conditions that have helped preserve them.