The Kostenets municipality (Bulgarian: Община Костенец) is one of the 22 municipalities of the Sofia Province, Bulgaria. Its territory is 302 km² and has 14,154 inhabitants as of 2009. It encompasses the Valley of Gorna Banya, along the upper flow of the Maritsa river, surrounded by Rila to the south and Sredna Gora to the north. The region has many warm mineral springs in the spa resorts of Momin Prohod, Momina Banya, Kostenets and Pchelinski Bani.