Osmanca is a neighborhood in Bigadiç District, in Balıkesir Province, Türkiye. Osmanca lies at 206 m above sea level, 4.2 km from the Alaçam Dağları mountains. It has 370 inhabitants. The nearest city is Paşa Alanı, 29 km to the northwest. Among the landmarks around are Çamköy Dam (3.0 km), Attea (4.7 km) and İkizcetepeler Dam (18.9 km).