Hausjärvi is a municipality of Finland. Its seat is in Oitti. It is located in the province of Southern Finland and is part of the Tavastia Proper region. The municipality has a population of 8,144 (31 December 2021) and covers an area of 398.77 square kilometres (153.97 sq mi) of which 8.98 km2 (3.47 sq mi) is water. The population density is 20.89 inhabitants per square kilometre (54.1/sq mi). The municipality is unilingually Finnish.