Lions are quite adaptable and can be found in a variety of different habitats like deciduous forests and semideserts but they prefer savannas, grassy plains, open woodlands and scrub country. They are never found in tropical rain forests or true deserts without any water.
The lion is found in parts of Africa south of the Sahara desert. Lions are the most social of all the felids, and live in organized groups called prides which can hold four to forty members. The pride is made up of related lionesses and their cubs and one to six males which have fought their way into the pride. If a lion is killed by another lion trying to join the pride, the previous male's cubs will be killed to give way for the new dominate lion's offspring. When a female comes to realize her cubs are gone, she goes into estrus and mates with the new dominate male. The pride is very social, and they often lick and rub heads with each other. The males are the protectors of the pride, and the females are the hunters and take care of the cubs.

Lions usually hunt at night or dawn. Their prey consists mainly of large mammals, such as antelopes, gazelles, warthogs, wildebeest, buffalos and zebras, but smaller animals like hares and birds are also taken occasionally. Carrion is readily taken and often recovered from other predators like hyaenas and wild dogs. In some areas lions specialise on rather untypical prey-species; this is the case at the Savuti river, where they constantly prey on young elephants, and at the Linyanti, where they hunt hippos (both rivers are in Chobe National Park, Botswana). It is reported that the lions, driven by extreme hunger, started taking down baby elephants, then moved on to adolescents and occasionally fully grown adults *.

Young lions first try hunting at three months old, but are often not successful hunters until they are two years old.

Lions can reach speeds of about 60 km/h (37 mph), but they don't have the endurance to be long-distance runners, so they have to come quite close to their prey before starting the attack. They sneak up to the victim until they reach a distance of about 30 m (98 feet) or less. Usually several lions work together and encircle the herd from different points. The attack is short and powerful and the lion tries to catch the victim with a fast rush and some final leaps. The prey is usually killed by a bite into the nape or throat.

Because lions hunt in open spaces, where they are easily seen by their prey, teamwork increases the likelihood of a successful hunt. Teamwork also enables them to defend their prey more easily against other large predators like hyenas, which can be attracted by vultures over kilometres in open savannas.
The males do not participate usually on hunting, except if very big animals like buffaloes are attacked.

An adult female lion needs about 5 kg (11 lbs) meat per day, a male ca. 7 kg (15 lbs).

Lions are predatory carnivores who manifest two types of social organization. Some are residents, living in groups, called prides. The pride consists of related females, their cubs of both sexes, and a group of one to four males known as a coalition who mate with the adult females. Others are nomads, ranging widely, either singly or in pairs.

Being smaller and lighter than males, lionesses are more agile and faster and do the pride's hunting, while the stronger males patrol the territory and protect the pride, for which they take the "lion's share" of the females' prey. When resting, lions seem to enjoy good fellowship with lots of touching, head rubbing, licking and purring. But when it comes to food, each lion looks out for itself. Squabbling and fighting are common, with adult males usually eating first, followed by the females and then the cubs.

Both males and females will defend the pride against intruders. Typically, males will not tolerate outside males, and females will not tolerate outside females. Males are expelled from the pride or leave on their own when they reach maturity.

Lions spend a lot of their time resting. They are inactive for about 20 hours per day.

The male lion, easily recognized by his mane, can weigh between 150-225 kg (330-500 lb), but usually most males average around 186 kg (410 lb) and females range from 120-150 kg (260-330 lb)•, and average around 125 kg (275 lb). Head and body length is 170 to 250 cm in males and 140 to 175 cm in females, shoulder height is about 123 cm in males and 100 cm in females. The tail length is 70 to 100 cm.
In the wild, lions live for around 10–14 years, while in captivity they can live over 20 years.

The coloration varies from light buff to yellowish, reddish or dark ochraceous brown. The underparts are generally brighter and the hairy tuft at the tip of the tail is black. The colour of the manes varies from blond to black.

The first lions are presumed to have been maneless. Until around 10,000 years ago, maneless forms seem to have persisted in Europe, and possibly the New World. The maned form may have appeared c. 320,000–190,000 years ago. This maned form may have had a selective advantage that enabled it to expand to replace the range of earlier maneless forms throughout Africa and western Eurasia by historic times. The mane has evolved due to sexually selective pressure driving the trait to an exaggerated point where it no longer serves any other function. The trait has reached the point where cost of maintaining the mane has begun to outweigh its benefits. In fact, lions with particularly large manes often have trouble with thermoregulation.

In the past scientists believed that the "distinct" subspecific status of some subspecies could be justified by their external morphology, like the size of their mane. This morphology was used to identify them, like the Barbary lion and Cape lion. However, now it is known that various extrinsic factors influence the colour and size of a lion’s mane, like the ambient temperature. The cooler ambient temperature in e.g. European and North American zoos can result in heavy mane. Therefore, the heavy mane is an inappropriate marker for identifying subspecies.

Maneless lions have been reported in Senegal and Tsavo-National Park. As well as having an inherited component, the presence, absence and degree of mane is also associated with sexual maturity and testosterone production. Castrated lions have minimal manes. The original male white lion from Timbavati was also maneless. Manelessness is also found in inbred lion populations; inbreeding also resutls in poor fertility. A heavy mane may provide an indicator of a lion's genetic and physical health. It may also afford him some protection in fights. In some animal species, females show a preference for males with better outward displays of fertility and vigour. It is possible that lionesses more actively solicit mating with heavily maned lions in prides led by a coalition of 2 or 3 males, though there seem to be no published studies.

Lions have also been known to breed with tigers (most often Amur and Bengal) to create hybrids called ligers and tigons. They have also been crossed with leopards to produce leopons and jaguars to produce jaglions. The marozi is reputedly a spotted lion or a naturally occurring leopon, while the Congolese spotted lion is a complex lion/jaguar/leopard hybrid called a lijagulep. Such hybrids were once commonly bred in zoos, but this is now discouraged due to the emphasis on conserving species and subspecies. Hybrids are still bred in private menageries and in zoos in China.

The liger is a cross between a male lion and a tigress. Because the lion sire passes on a growth-promoting gene, but the corresponding growth-inhibiting gene from the female lion is absent, ligers grow larger than either parent. They share physical and behavioural qualities of both parent species (spots and stripes on a sandy background). Male ligers are sterile, but female ligers are often fertile.

The less common tigon is a cross between the lioness and the male tiger. Because the male tiger does not pass on a growth-promoting gene and the lioness passes on a growth inhibiting gene, tigons are often relatively small, only weighing up to 150 kilograms (350 lb), which is about 20% smaller than lions. Like ligers, they have physical and behavioural traits from both parental species and males are sterile.