Somero is a town and municipality located in the Southwest Finland region within the province of Western Finland. It is situated approximately 36 kilometres northeast of Salo, 86 kilometres east of Turku, and 105 kilometres northwest of Helsinki.
The municipality covers an area of 697.67 square kilometres, which includes 29.9 square kilometres of water. It has a population of 8,339 people, resulting in a population density of 12.48 inhabitants per square kilometre. The municipality is unilingually Finnish.