Radiocarbon dating, a scientific method of dating once-living matter

RCD Mallorca

Residual-current device in electrical engineering, a 'safety switch' style mechanism to prevent electrocution

RCD Espanyol de Barcelona

RC Deportivo de La Coruña

Rye Country Day School in New York, United States

Rassemblement Congolais pour la Démocratie, a rebel group in the Democratic Republic of the Congo

The Royal Canadian Dragoons, a Canadian Forces armoured regiment

Rabbit calicivirus, a virus that causes Rabbit Haemorrhagic Disease

Rally for Culture and Democracy, a political party in Algeria

Rassemblement Constitutionnel Démocratique, a political party in Tunisia

Spanish Real Club Deportivo or Catalan: Reial Club Deportiu, various football clubs: