The Erms (German pronunciation: [ˈɛʁms] ⓘ) is a river of the karstified Swabian Alb range in Baden-Württemberg, Germany.

On its way from the Karst spring to the next large municipality Bad Urach, a former Erms sedimented, especially during floods, no less than eight valley cataracts, where chemically precipitated travertine repeatedly drops c. 2 to 5 metres (7 to 16 ft).

The longitudinal profile, stepped by limestone sinter deposits, was once more conspicuous than today due to several natural reservoirs and favoured the industrial development along the river because of the easily usable water power.

Between Seeburg and Bad Urach the river Erms flows through the upper Ermstal, which here forms the Border of the villages Wittlingen and Sirchingen.

The valley section is characterized by the closely opposite, wooded slopes of the Albtrauf, crowned by limestone rocks.

Since the limestone tuff (precipitated lime) is a good building material that is easy to extract, the lakes gradually disappeared.

Here, from the east, the multi-branched valley system of the Elsach, whose sources lie in the Falkensteiner Höhle and in the Elsachbröller, flows out.

After the river has passed Bempflingen, it flows into the Neckar at Neckartenzlingen, whose waters reach the North Sea via the Rhine.

The river Erms drains an area of about 179 km2 (69 sq mi), mainly in the middle Swabian Alb and its foreland.