Democritus is an oil on canvas painting by Jusepe de Ribera, executed in 1630, now in the Museo del Prado, in Madrid.

It could then be the painting known as Philosopher with Compass, a work whose whereabouts is unknown and is known to have belonged to the Duke of Alcalá, Ribera's main client between 1629 and 1631.

A light enters from the left, bathing the philosopher's body, which together with a halo of lighter paint around the head and the neutral background highlights him, giving the composition a greater perspective and realism.

It is believed that Ribera had a model pose for the picture, possibly someone anonymous found on the street, whom he portrayed as if he were a nobleman or a king.

Nícola Spinosa defines it in the study of his work: "A true portrait of any peasant found in the alleys of viceregal Naples, in which the painter knew how to capture precisely the signs of the ancient Greco-Levantine origin, inserted in a context of irreducible vitality and typically Mediterranean humanity.