Inside the Warriors universe, most Cats are divided into five Clans: ThunderClan, ShadowClan, WindClan, RiverClan, and SkyClan. Deceased cats who generally followed The Warrior Code and were believers in the Clans' religion went to StarClan. If they made mistakes but believed they were doing what was right then they usually still join StarClan when they die. Cats that did not follow The Warrior Code do not go to StarClan and instead join The Dark Forest. SkyClan, the fifth Clan, was driven from their territory when it was destroyed by twolegs and now are separated from the other four. BloodClan was not really a Clan but more a group of cats banded together for strength in numbers.
RiverClan is best known for their skill at swimming and being the only Clan comfortable around and in water. They are also recognised for their unique ability of scooping fish from the river. Their very first Leader was Riverstar and their current cannon Leader is Mistystar.
ThunderClan is the most heavily featured Clan in both the cannon and fannon. They are best known for their skill of hunting and fighting in dense undergrowth. Their very first Leader was Thunderstar and their current cannon Leader is Bramblestar.
ShadowClan is the source of most of the evil cats in the series. They are best known for their ability to walk silently and undetected. They are also recognised for their ability to eat anything. Their very first Leader was Shadowstar and their current cannon Leader is Rowanstar.
SkyClan is was the fifth Clan of The Forest and was introduced in Firestar's Quest. When they left The Forest, it severed their ties with the other Clans and almost wiped them out. They are best known for their ability to jump considerable heights and hard, grey pads that help them walk long distances on rough surfaces, like tree branches and rocks.
BloodClan is an unofficial Clan. Its only known members are Scourge, Ice, Snake, Bone, Jaggedtooth, and Brick. Its laws also differ from the other Clans since they have no Warrior Code and do not believe in StarClan.