John Ernest, Duke of Saxe Coburg

John Ernest (German: Johann Ernst) (10 May 1521 – 8 February 1553) was a Duke of Saxe-Coburg.

John Ernest was born in Coburg as the third (but second surviving and the youngest) son of John, Elector of Saxony, and his second wife Margaret of Anhalt-Köthen. After the death of his father (1532), his half-brother, John Frederick I, assumed the title of Elector of Saxony; John Ernest took part with him in the rule over the Electorate of Saxony.

In 1542 John Frederick I decided to rule alone, and ceded to John Ernest the Franconian areas of the Wettin family lands (Coburg, Eisfeld, etc.); but it was not until 1547 (after the Battle of Mühlberg) when John Ernest could govern undisturbed in Coburg. He married Catherine, daughter of Philip I, Duke of Brunswick-Grubenhagen, but the marriage was childless. After his death in Coburg, the city fell for a few months to John Frederick — dismissed from the imperial detention — before his death, and then, to his three sons, which governed the Ernestine lands together from 1554 for some years.