Schwarzensee, Mountain lake in St. Wolfgang im Salzkammergut, Austria.

Schwarzensee is a kidney-shaped mountain lake at 716 m above sea level on the eastern foot of the Schafberg, about 2 km northwest of Rußbach in the municipality of St. Wolfgang im Salzkammergut. It is 1.4 km long, up to 400 m wide and reaches a maximum depth of 57 m. The southwest shore is flat, while the northeast banks are rocky and steep; alpine pastures such as the Gramerhauseralm, Simmerlalm and Bacherlalm surround the water.

The Schwarzensee basin was carved by a side branch of the Traungletscher, which left late-glacial clays that dam the water. Since 1965 the lake and its surroundings have been a protected area. A 110 kV power line built in 1963/64 crosses the water surface in the northwest. The lake is privately owned but open to the public.

The lake lies in a nature reserve, yet sport fishing is permitted there. Boating is stricter than elsewhere in the Salzkammergut: not only combustion engines but all craft, including rowing boats, canoes and kayaks, are banned on the water. Anglers share the shore with walkers and bathers.

Access is by the Schwarzenseestraße L1293 from Strobl via Russbach, ending at a car park about a kilometre from the shore; only guests with accommodation may drive to the bank. A forest road circles the lake but is closed to public traffic. Boats of any kind, including rowing boats and kayaks, are banned.

A loop trail of nearly 10 kilometers circles the water and connects several mountain inns along the way. The route gains about 400 meters in elevation and offers repeated views of the lake and surrounding peaks.