Larsmo (Finnish: Luoto) is a municipality of Finland, located in the Ostrobothnia region of the province of Western Finland.
"Larsmo" is also the name of one of the villages in the municipality of Larsmo. The municipality is bilingual with Swedish as the majority language and Finnish as the minority language. Until 2014 Swedish was Larsmo's only official language. The municipality and consists of an archipelago of about 360 islands and numerous skerries. The length of the coastline is about 500 kilometres (310 mi). Lake Larsmo (Larsmosjön), which is Finland's largest artificial fresh water lake is also located in the municipality.
The municipality has a population of 5,136 (30 June 2015) and covers an area of 853.51 square kilometres (329.54 sq mi) of which 711.07 km2 (274.55 sq mi) is water. The population density is 36.06 inhabitants per square kilometre (93.4/sq mi).
The land, which was to become Larsmo rose from the sea some 2,000 years ago, due to post-glacial rebound. Today the municipality consists of more than 360 islands.