Description Leo () is the fifth astrological sign of the Zodiac, originating from the constellation of Leo. In astrology, Leo is considered to be a 'masculine', positive (extrovert) sign. It is also considered a fire sign and is one of four fixed signs.In Greek mythology, the constellation of Leo is explained through the tale of Heracles and the Nemean lion. More than a lion, this beast was the sibling of the infamous Sphinx whom Oedipus encounters. The creature had terrorized the countryside for years and all weapons were useless against it. Hercules was sent to kill the beast by Hera; as an illegitimate son of Zeus the goddess hated him and hoped for his failure. Hercules, however, proved successful in defeating the Nemean Lion, literaly wearing his victory by making a cloak and helmut from the creature's hide. In honor of this great feat, Zeus set the form of the fearsome Lion in the night sky.