Leo constellation from from Petrus Apianus, Cosmographia, 1529. Leo is one of the constellations of the zodiac. Its name is Latin for lion. One of the 48 constellations described by the 2nd century astronomer Ptolemy, and it remains one of the 88 modern constellations defined by the International Astronomical Union. Leo was one of the earliest recognized constellations, with archaeological evidence that the Mesopotamians had a similar constellation as early as 4000 BC. Leo is the fifth astrological sign of the zodiac, originating from the constellation of Leo. It spans the 120-150th degree of the Tropical zodiac, between 125.25 and 152.75 degree of celestial longitude, which the Sun transits this area on average between July 23 to August 22 each year.