Karjalohja (Finnish pronunciation: [ˈkɑrjɑˌlohjɑ]), or Karislojo in Swedish, is a former municipality of Finland.

It is located in the province of Southern Finland and is part of the Uusimaa region. The municipality has a population of 1,474 (31 December 2012) and covers an area of 163.40 square kilometres (63.09 sq mi) of which 42.11 km (16.26 sq mi) is water. The population density is 12.153/km (31.475/sq mi).