Irrsee is a lake in the Salzkammergut, Austria, located at 47°54′44″N 13°18′25″E / 47.91222°N 13.30694°E / 47.91222; 13.30694. Its surface is approximately 3.5 km (1.4 sq mi) and its maximum depth is 32 metres. It is a popular tourist destination, also thanks to the warmest water temperature of all lakes in Salzkammergut. It is drained by the Zeller Ache towards the Mondsee.