Nousiainen (Swedish: Nousis) is a municipality in the region of Lounais-Suomi. It is Located in the Southwest Finland region. The Finnish-speaking municipality has a population of 4,733 (31 January 2019) and covers an area of 199.55 square kilometres (77.05 sq mi) of which 0.62 km2 (0.24 sq mi) is water. The population density is 23.81 inhabitants per square kilometre (61.7/sq mi).
Nousiainen was the first seat of the bishop of Finland until the early 13th century, whereafter the seat was shifted to Turku. It remained, however, a place of pilgrimage throughout the Middle Ages. The coat of arms of Nousiainen depicts Bishop Henry and Lalli.