Harjavalta (Finnish pronunciation: [ˈhɑrjɑˌʋɑltɑ]) is a town and municipality in Finland. It's located in the Satakunta region, 29 kilometres (18 mi) southeast of Pori. The town has a population of 6,656 (31 October 2024) and covers an area of 127.74 square kilometres (49.32 sq mi) of which 4.28 km2 (1.65 sq mi) is water. The population density is 53.9 inhabitants per square kilometre (140/sq mi).
Harjavalta is a centre for copper and nickel smelting industries. Today's most used metal recovery method, the flash smelting method, was developed at Harjavalta and implemented in 1949. Originally part of Outokumpu, a Finnish company, the local copper business is now owned by Boliden and the nickel business by Norilsk Nickel.
Hiittenharju is a ridge in Harjavalta, known for its archaeology and cultural history. The banks of the ancient Litorina Sea lies on the fringes of the Hiittenharju ridge. In the Hiittenharju area Bronze Age graves, called barrows, have been discovered, and there is also a historical route called Huovintie running through Hiittenharju. The river Kokemäenjoki river runs through the town.
The neighboring municipalities are Eura, Kokemäki, Nakkila and Ulvila. The municipality is unilingually Finnish.