Lohtaja (Swedish: Lochteå) is a former municipality of Finland. Lohtaja was condolidated with the city of Kokkola on January 1 2009.
It is located in the province of Western Finland and is part of the Central Ostrobothnia region. The former municipality had a population of 2,900 (2003) and covered an area of 289.26 km² of which 3.33 km² was water. The population density was 10.0 inhabitants per km². The municipality was unilingually Finnish.
Lohtaja is popular for its coastline, Vattajaniemi, which is the longest beach in Scandinavia. However, the coastline is partly used by the military as a drill-area. An association called Pro Vattaja was founded to campaign for the area to be saved for civil use.