The Bolshaya Synya, also known simply as Synya, is a river in the Komi Republic, Russia. The river is 206 kilometres (128 mi) long —249 km (155 mi) from the source of the Voyvozh-Synya at its head— and has a catchment area of 4,040 square kilometres (1,560 sq mi). The Synya Formation, a Middle Triassic geological formation, is named after the Bolshaya Synya river.