The Enns is a southern tributary of the river Danube, joining northward at Enns, Austria. It forms much of the border between the states of Lower Austria and Upper Austria. The Enns spans 253 kilometres (157 mi), in a flat-J-shape. It flows from its source near the village Flachau, generally eastward through Radstadt, Schladming, and Liezen, then turns north near Hieflau, to flow past Weyer and Ternberg through Steyr, and further north to the Danube at Enns.

Enns is a town in the Austrian state of Upper Austria on the river Enns, which forms the border with the state of Lower Austria.