Leo, a constellation and the fifth sign of the zodiac. The name means The Lion. Leo is bordered on the north by Leo Minor and Ursa Major, on the east by Cancer, on the south by Crater and Sextans, and on the west by Coma Berenices and Virgo. The constellation contains about 100 stars that can be seen with the unaided eye. Brightest is Alpha Leonis, also called Regulus and Cor Leonis.