Leo
Leo is a Zodiacal constellation otherwise known as the Lion. It is one of the 48 Greek constellations originally described by the 2nd century astronomer Claudius Ptolemy (Wikipedia). Leo remains one of the 88 modern constellations defined by the International Astronomical Union (Wikipedia).
Leo (abbrev. = Leo; genitive = Leonis) covers 947 square degrees or 2.30% of the celestial sphere making it the 12th largest constellation. It contains 123 stars brighter than apparent magnitude 6.5, the brightest star being Regulus (Alpha Leonis). See Leo for a photo this constellation from Bifrost Observatory.
An image of the 2012 conjunction of Mars in Leo can be seen at Leo and Mars.
For more information see the entries for Leo at Wikipedia and U. Wisconsin. For a chart of Leo, see Leo (IAU).