What was the guardian spirit of a Roman man called?

The guardian spirit of a Roman man was called his genius.

In Roman religion, a genius was a divine spirit associated with an individual male and believed to accompany him from birth until death. It represented the person’s generative power, character, and connection to the divine rather than simply an intellectual talent, which is the main modern meaning of “genius.”

Romans could honor a man’s genius in household and personal rituals. The genius of the head of a household was especially important, and images of genii were sometimes shown as youthful, winged, or human-like protective figures. The plural form is genii.

The concept was broader than individual guardianship. Places, institutions, festivals, vineyards, theaters, and other things could possess a genius loci, or “spirit of the place.” Women were traditionally associated with a corresponding protective spirit called a Juno. Lar and Penates are related household divinities, but neither is the specific guardian spirit of a Roman man.