Kolonjärvi is a lake located in Keuruu in central Finland, which belongs to the Kokemäenjoki watershed. It has an area of 239 hectares (590 acres), and a coastline of some 12 kilometres (7.5 mi).

According to data from the Finnish Environment Institute, the lake contains a total of 13 islands of various sizes, totaling approximately 4.8 hectares (12 acres). It has a mean depth of 4.32 metres (14.2 ft), with a maximum depth of 14.83 metres (48.7 ft)