Joachim Ernest of Anhalt (21 October 1536 – 6 December 1586), was a German prince of the House of Ascania, ruler of the principality of Anhalt-Zerbst from 1551, and from 1570 sole ruler of all the Anhalt lands.
Joachim Ernest was born in Dessau on 21 October 1536 as the second son of John V, Prince of Anhalt-Zerbst, by his wife Margaret, daughter of Joachim I Nestor, Elector of Brandenburg. He received an extensive education under the supervision of his father. On 1 February 1549, just thirteen years of age, he was officially admitted to the University of Wittenberg, where, among others, he studied with the theologian Georg Helt.
In 1550, after the death of his father, he inherited Anhalt-Zerbst along with his older brother Karl I and his younger brother Bernhard VII.
The death of his uncle George III without male heirs permitted him and his brothers, Karl I and Bernhard VII, to inherit Anhalt-Plötzkau in 1553, while the death of his uncle Joachim I permitted him and his surviving brother Bernhard VII to inherit Anhalt-Dessau in 1561. In 1562 his cousin Wolfgang abdicated Anhalt-Köthen in his favor.
In Barby on 3 March 1560 Joachim Ernest married Agnes (b. Barby, 23 June 1540 – d. Bernburg, 27 November 1569), daughter of Wolfgang I, Count of Barby-Mühlingen. They had six children.