Bartasiškis is a village in Biržai District Municipality, in Panevėžys County, Lithuania. Bartasiškis lies at 69 m above sea level. The nearest city is Panevėžys, 51 km to the southwest. Among the landmarks around are Biržai Castle (7.4 km), Church of the Assumption of Mary in Skaistkalne (29 km) and Lutheran church in Nereta (34 km). Among the natural features are Cow cave (9.4 km).