Lake Baluošas is one of the most distinctive lakes of Aukštaitija National Park in northeastern Lithuania, lying about 8.5 km northwest of Ignalina. A glacial channel lake, its basin was carved as two parallel troughs separated by an underwater ridge, giving it a highly indented shoreline that stretches over 15 km. The lake runs 4.85 km from northwest to southeast and reaches 1.34 km in width, with tree-covered banks surrounded by the old Ažvinčiai–Minčia forest.

Baluošas holds eight wooded islands, and one of them — Ilgasalė — is unique in Lithuania: the island contains its own small lake, connected to Baluošas by a narrow channel. The Būka River feeds the lake from the north, while the Kragžlė stream drains it southward into the Žeimena river basin. The surrounding shores, rich in lake chalk, support Lithuania's greatest concentration of wild orchids, and the whole area is protected as the Baluošas Landscape Reserve, dotted with old ethnographic villages such as Šuminai and Trainiškis.