Balıkesir Province is a province and metropolitan municipality in northwestern Turkey with coastlines on both the Sea of Marmara and the Aegean. Its area is 14,583 km2, and its population is 1,257,590 (2022). Its adjacent provinces are Çanakkale to the west, İzmir to the southwest, Manisa to the south, Kütahya to the southeast, and Bursa to the east. The provincial capital is Balıkesir. Most of the province lies in the Marmara Region except the southern parts of Bigadiç Edremit, Kepsut, İvrindi, Savaştepe and Sındırgı districts and ones of Ayvalık, Burhaniye, Dursunbey, Gömeç and Havran, that bound the Aegean Region. Kaz Dağı, known also as Mount Ida, is located in this province. Balıkesir province is famous for its olives, thermal spas, and clean beaches, making it an important tourist destination. The province also hosts immense deposits of kaolinite and borax, with some open-pit mines. The Kaz mountains are also threatened with the expansion of gold mining using cyanide which puts the villagers' lives, the agricultural economy, and tourism at risk.

The Sea of Marmara, also known as the Sea of Marmora or the Marmara Sea, is a small inland sea located entirely within the borders of Turkey. It connects the Black Sea to the Aegean Sea via the Bosporus and Dardanelles straits, separating Turkey’s European and Asian sides. It has an area of 11,350 km2 (4,380 sq mi), and its dimensions are 280 km × 80 km. Its greatest depth is 1,370 m (4,490 ft).