OCG

OCG may refer to:


 * Operation Clean Government, a citizens' lobby and advocacy organization in the United States
 * Orchestre de chambre de Genève, a Swiss orchestra
 * City of Granada Orchestra (Orquesta Ciudad de Granada), a Spanish orchestra
 * Organized crime group
 * Orthodox Church of the Gauls
 * Occipital gyri (OcG), a structure in the brain