An equestrian portrait of Prince Baltasar Carlos (1629-1646), son of Felipe IV (1605-1665) and Isabel de Bourbon (1603-1644), bearing the staff of command and wearing a general's sash. The mountains of Madrid are visible in the background. He was the King's first male son and his early death left Spain without a male heir until the birth of the future Carlos II (1661-1700).

This work was painted for the Hall of Kingdoms at Madrid's Buen Retiro Palace, where it was hung over a door between the equestrian portraits of the Prince's parents, in keeping with the idea of dynastic continuity that the iconographic program sought to reflect. The fact that the painting was intended to hang at such a height explains its strange perspective, especially the anatomic composition of the horse, as it was intended to be seen from below.

The very fresh and loose technique is especially impressive in the boy's face, making this one of Velazquez's best portraits.