Which ancient Roman architect inspired Leonardo's Vitruvian Man?

The ancient Roman architect who inspired Leonardo’s Vitruvian Man was Vitruvius. Leonardo based the drawing on Vitruvius’s discussion of ideal human proportions in De architectura, his ten-book treatise on architecture.

Vitruvius described how a well-proportioned human body could fit within both a circle and a square. Leonardo illustrated and refined that idea in a drawing usually dated to around 1490, showing one nude male figure in two superimposed positions. The navel serves as the circle’s center, while the square is positioned differently so the geometry works with the body’s proportions.

Leonardo did not simply copy Vitruvius. He compared the ancient description with his own anatomical observations and other Renaissance writings, correcting or adapting several measurements. The drawing’s full title refers to the proportions of the human body according to Vitruvius. It is now held by the Gallerie dell’Accademia in Venice and is displayed only rarely because light can damage the paper. Cicero, Seneca, and Pliny were Roman authors, but none was the architectural source behind this famous image.