Casu

Casu is the Sardinian word for cheese. In the Sardinian language, casu is the general term for cheese and appears in the names of traditional cheeses as well as in everyday speech. The word derives from the Latin caseus, reflecting Sardinia’s historical linguistic ties to Italic and Romance languages; cognate terms include Italian formaggio, Spanish queso, and French fromage.

The most well-known cheese associated with the term is casu marzu, a shepherd’s cheese made from sheep milk that is intentionally infested with the larvae of the cheese fly Piophila casei. The larvae digest fats and proteins, producing a very ripe, soft cheese that may contain visible larvae. Casu marzu has cultural importance in Sardinian rural life but is subject to food-safety laws in many jurisdictions; its sale is restricted or banned in the European Union, though it remains valued and may be produced for local consumption under specific conditions in some areas.

Beyond casu marzu, the Sardinian culinary tradition uses casu in the broader discourse of cheese, and cheese plays a central role in regional markets and rural life. The term remains a living element of Sardinian language and cuisine, reflecting the island’s long history of sheep farming and dairy production.