Laihia is a municipality of Finland, founded in 1576 through a separation from Isokyrö and Korsholm.
It is located in the Ostrobothnia region. The municipality has a population of 7,999 and covers an area of 508.44 square kilometres of which 4.14 km2 is water. Laihia consists of 37 villages.
Laihia is within the economical region of the neighbouring city Vaasa. The municipality is unilingually Finnish. Only 79 people speak Swedish as a native language. Most inhabitants speak Finnish or a dialect typical of this region. The municipal manager is Juha Rikala. There are a total of 469 farms in the municipality.
Laihia is located along the international tourist route Blue Highway, which goes from Norway to Russia via Sweden and Finland.