Der Ister is a poem by Friedrich Hölderlin

Der Ister (German for The Ister) (now known as the Danube) can mean:

Hölderlin's Hymn "The Ister" (Ger: Hölderlins Hymne >>Der Ister<<) is the title given to a 1942 lecture course by German philosopher Martin Heidegger.

The Ister is a 2004 film about Heidegger's philosophy and the river itself taking its name from the lecture course