The Ister

Ister, The Ister, or Der Ister may refer to:
 * The Danube river, known as the Ister in Latin and Istros (Ἴστρος) in Ancient Greek and Thracian
 * The Dniester river, known as the Ister in Thracian
 * "Der Ister", a poem by Friedrich Hölderlin
 * Hölderlin's Hymn "The Ister", a lecture course delivered by Martin Heidegger in 1942
 * Ister-class frigate, a group of screw frigates ordered for the Royal Navy in the early 1860s
 * The Ister (film), a 2004 film directed by David Barison and Daniel Ross
 * Tajuria ister, a butterfly of the family Lycaenidae