The lion (Panthera leo) is a member of the family Felidae and one of four "big cats" in the genus Panthera. Reaching up to 225 kg (500 lb), the lion is eclipsed in size by the tiger amongst felines, and both are significantly larger than any other cat. Although lions were once widespread throughout much of Africa, Asia, and Europe, they currently exist in the wild only in Africa, with a critically endangered remnant population in India. As a whole, the species is listed as "vulnerable"; it has seen a significant and possibly irreversible decline in numbers in its African range.

In the wild, lions live for approximately 10–14 years, while in captivity they can live over 20 years. Today lions are found only in tropical climates, but during the Ice age, they penetrated far north (even to Bering land bridge). They typically range across savanna and grassland, although they may take to bush and forest. It is an apex and keystone predator. Unusually for a cat, lions hunt together. Groups of female lions typically bring down prey, mostly large ungulates. The lion pride consists of related females and offspring and a small number of resident males. Lions are territorial and the pride, though not strictly hierarchical, is dominated by an adult male or coalition of males.

The male lion is highly distinctive and usually instantly recognized by its mane. The lion, particularly the face of the male, is one of the most widely recognized animal symbols in human culture. It has been extensively depicted on sculptures, in paintings, on national flags and in films.
The Lion has been an important symbol for thousands of years and appears as a theme in cultures across Europe, Asia and Africa. Despite the recorded incidents of attacks on humans, lions enjoy positive depiction in pop culture as creatures that appear strong but gentle at the same time. The most consistent depiction is in keeping with their image of "king of the jungle" or "king of the beasts", hence the lion is a popular symbol of royalty and stateliness and a symbol of bravery.

The lion is a common charge in heraldry, traditionally symbolizing courage. The following positions of heraldic lions are recognized:
rampant
guardant
reguardant
 passant
statant
couchant
 salient
sejant
dormant

The lion holds historical significance for English heraldry and symbolism. The Three Lions was a symbol for Richard the Lionheart, and later, for England. For many centuries the lion had been a feature of the Armorial of Plantagenet of the House of Plantagenet.

The Lion Rampant continues to be used widely today; the Royal Standard of Scotland has given rise to its use as the emblem for the Scotland national football team and Rangers and Dundee United of the Scottish Premier League, as well as Aston Villa in the English Premier League; and not only sport but businesses such as the French car company Peugeot. Though the Lion Rampant appears on the Lyon coat of arms and flag, the French city's name has an unrelated derivation despite the similarity.