An equestrian portrait of Emperor Carlos V (1500-1558) commemorating the victory of imperial troops over the Protestants at Mühlberg. The apparently straightforward composition hides a complex symbolism that portrays Carlos as both a Christian knight and heir to the imperial tradition of Rome. For example, the lance he holds in his right hand symbolizes the power of the Caesars, but it simultaneously alludes to Saint George's weapon, and to the one carried by Longinus during the Passion of Christ (Longinus was a Roman soldier who speared Christ in the ribs and then became a Christian).

The formal forerunners to this composition have been seen in the Roman statue of Emperor Marcus Aurelius (121-180) on Horseback, and various models of engravings by Albrecht Dürer, including The Knight and Death, as well as engravings by Hans Burgkmain.

The armor worn by the Emperor in this painting is now in the Royal Armory at Madrid's Royal Palace.

This work was made for Maria of Hungary and became the epitomal image of the Hapsburg dynasty. It entered the Prado Museum's collection in 1827.