Leopold IV Frederick, Duke of Anhalt (1 October 1794 – 22 May 1871) was a German prince of the House of Ascania.

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.^[1]

Following the death of his grandfather Leopold III he succeeded as duke on 9 August 1817.^[1]

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 It was revoked, however, on 4 November 1849, then replaced with a new version in October 1859.^{[citation needed]} Leopold maintained a friendship with his administrative officer Wilhelm Christian Raster, though Raster's politically active son, Hermann participated in the revolutions.^[2] The younger Raster was given the unusual choice to either stay in Anhalt-Dessau and face criminal prosecution for his role in the Revolution or to emigrate from the country freely like other Forty-Eighters. Raster made the second choice and eventually became a powerful Republican Party political boss in the United States.^[3]

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.^[1] 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.^[1] On 30 August he assumed the title "duke of Anhalt."^[1]

Leopold died in Dessau on 22 May 1871. He was succeeded by his son Frederick.^[4]

In Berlin on 18 April 1818 Leopold married Princess Frederica of Prussia (b. Berlin, 30 September 1796 - d. Dessau, 1 January 1850), daughter of Prince Frederick Louis Charles of Prussia (brother of King Frederick William III of Prussia) by his wife Frederica of Mecklenburg-Strelitz; through her mother's last marriage, she was a half-sister of King George V of Hanover.^[1] They had been engaged since 17 May 1816, as the connection had already been arranged by the Prussian court. This dynastic connection was an expression of Leopold's pro-Prussian policies.

They had six children:^{[5][6][better source needed]}

He received the following orders and decorations:^[7]