Leo is the fifth sign, fixed, fiery and the only sign ruled by the Sun, and it has no exaltation assigned to it in the standard scheme, an absence the tradition explains by saying the Sun needs no dignity beyond its own house. It occupies the height of summer, and the classical reading follows the season: heat at its most settled, light at its most abundant, and a quality the sources describe as royal, from the figure as much as from the ruler. Leo is one of the four signs the tradition calls bestial or feral, and one of the four whose fixed character was later attached to the four living creatures of Ezekiel and Revelation, giving the lion of that vision to this sign. The solar rulership carries with it the older correspondence of the Sun to the heart, to gold, and to the ruler of a state.
Leo's three decans run Saturn, Jupiter, Mars, a notably harder sequence of planets ruling a fire sign than the sign's own solar warmth would suggest, and the contrast was noted by Renaissance decan literature as a case where the ruling planet of a face and the sign it falls in can pull in quite different directions. As a fire sign Leo's triplicity rulership is one of the points on which Ptolemy and Dorotheus's table agree exactly, Sun by day and Jupiter by night, unlike the water triplicity's genuine dispute; the fire, earth and air triplicities all show this same cross-authority agreement, leaving the water signs as the one element where the classical sources diverge.