Caso (Asturian: Casu) is a municipality in the Spanish Principality of Asturias. It shares a boundary to the North with Piloña; to the East with Ponga; to the South with León and to the West with Sobrescobio and Laviana.
Most of the inhabitants of Caso live in the Nalón Valley, on which the largest town is the capital El Campu. The town is divided in two neighbourhoods: L'Arrobiu and El Barru.
The municipalities of Caso and Sobrescobio together constitute the Redes Natural Park, designated by the UNESCO as a Biosphere Reserve. The Natural Monument of the Cueva Deboyu (the Nalón River passes through a cave in the mountain) is also located in Caso. Caso is famous for its landscape, European beech forests, wood handcraft and its Casín cheese.
In the past, most of Caso's people worked in coal mining and livestock farming. Nowadays, tourism has become one of the more important activities in Caso, but farming is still the most relevant.
The Dam of Tanes provides electric energy and drinking water to the central part of Asturias.
The AS-17 (Avilés - Pass of Tarna) road is the easiest form to reach Caso from Oviedo or Gijón. The AS-254 (El Campu - L'Infiestu) road connects Caso with Piloña and the N-634 road. Caso and León are connected by the Pass of Tarna. The nearest train station is located in Pola de Laviana.
- 24 June, Saint John the Baptist, El Campu
- 25 July, Saint James the Great, Bueres
- 8 August, Harvester's Feast, Caliao
- Last weekend of August, Casín Cheese's Contest, Collada de Arnicio (Gobezanes)
- 8 October, Cattle Market and Contest, El Campu
- Museo de la Madera y la Madreña (wood handcraft museum), in Veneros
- Taller de la Madera y la Madreña (wood handcraft workshop), in Pendones
- Redes Visitor Centre, in Campo de Caso
- Arrudos Defile, in Caleao
- Deboyu Cave, in Campo de Caso
- Mongayu Cascades, in Tarna
- Brañagallones (shepherd's huts in the mountain), in Bezanes
- Pandu Quarter (traditional asturian architecture), in Campo de Caso
- Santa Maria la Real Church (16th century), in Tanes
- Santa Cruz de la Real Church (Baroque altarpiece), in Caleao