Sipoo (Finnish pronunciation: [ˈsipoː], Swedish:Sibbo) is a municipality of Finland. Its seat is in Nikkilä/Nickby. It is the eastern neighbour of Helsinki and is located in the Uusimaa region. The municipality has a population of 19,528 (31 March 2016) and covers an area of 698.59 square kilometres (269.73 sq mi) of which 358.97 km (138.60 sq mi) is water. The population density is 57.5 inhabitants per square kilometre (149/sq mi).