From 1817 until 1853 he was ruler of the duchy of Anhalt-Dessau and from 1847 until 1853 also ruler of the duchy of Anhalt-Köthen. From 1853 until 1863 he was the ruler of the joined duchy of Anhalt-Dessau-Köthen and from 1863 the first ruler of the united duchy of Anhalt.

Leopold was born in Dessau on 1 October 1794 as the eldest son of Frederick, Hereditary Prince of Anhalt-Dessau, by his wife Landgravine Amalie of Hesse-Homburg, daughter of Frederick V, Landgrave of Hesse-Homburg.

Following the premature death of his father in 1814, he became heir to the duchy of Anhalt-Dessau.

Following the death of his grandfather Leopold III he succeeded as duke on 9 August 1817.

The Duke's Administrative Officer and close friend was Christian Raster, a German statesman.

During the revolutions of 1848 he was forced to grant a constitution to Dessau on 29 October 1848. It was revoked, however, on 4 November 1849, then replaced with a new version in October 1859.

On 27 November 1847 he inherited the Duchy of Anhalt-Köthen from his distant cousin Duke Henry. As a result of a treaty concluded with Anhalt-Bernburg in May 1853 his duchies were joined together and named Anhalt-Dessau-Köthen, because the eventual inheritance of Leopold over all the Anhalt duchies seemed inevitable. The death of another distant cousin, Duke Alexander Karl, on 19 August 1863 resulted in the ruling line of the duchy of Anhalt-Bernburg becoming extinct, thus Leopold inherited that duchy as well. On 30 August he assumed the title "duke of Anhalt."

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