Pyhäjoki is a municipality of Finland. It is located in the defunct province of Oulu, which was split in two regions; Pyhäjoki is part of the Northern Ostrobothnia region.

The municipality is located on the Gulf of Bothnia at the mouth of the river Pyhäjoki. It has a population of 3,259 (30 June 2015) and covers an area of 1,365.31 square kilometres (527.15 sq mi) of which 823.25 km (317.86 sq mi) is water. The population density is 6.01 inhabitants per square kilometre (15.6/sq mi). The municipality is unilingually Finnish.