An official screenshot of lions that were added in the 1.6 vanilla Minecraft update, along with horses.
Lions are neutral mobs that hunt passive mobs and attack players that get too close, they are roughly as common as an enderman, placing them in the category of Uncommon, and spawn in groups of 4-8 exclusively in Savannahs. Lions have 15 hearts and are untamable save for the cubs which have a 25% chance to spawn. Cubs, like all other big cats, can be tamed if fed 5-10 bones or 2-4 raw pork, chicken or beef, you must then place a Cat Collar on the said cub and name it. They have a standing, Sleeping and sitting position.
Characteristics
During the day, Lions enter 'sleep mode' under small trees if the player gets to close or attacks, they will wake up and attack. At night they hunt passive mobs and players. Tigers are quite tall, roughly the size of the player in terms of height and being 3 blocks long, in their sitting position they are 1 and a half blocks long and 2 blocks high. They can run twice as fast as the player.
Taming and Breeding
As stated before lion cubs can be tamed by feeding them specific things and then being given a cat collar. Lions grow to full size in 7 minecraft days, they can be healed by being fed cat food, raw pork, beef or chicken. Right clicking them will make them sit.
Breeding involves feeding 2 full grown lions Cat Hearts which will initiate love mode. lions require a pen at least 3x3x3 to breed, with no players within 10 blocks of them. Breeding a lion and a tiger may produce a Liger (1 in 10 chance).