The cat-like aliens from the ThunderCats universe.
The Thunderians are a cat like alien species who were once in the service of Mumm-Ra, the Cats rebelled against Mumm-Ra alongside the other animal people and were stranded on Third Earth, where they and other aliens enslaved by Mumm-Ra made a new home. Over centuries the fact that the Cats once served Mumm-Ra was forgotten until Lion-O activated the Book of Omens.
It is unknown if their original home planet still exists in the current series (in the original series it was destroyed)
The Thunderians resided in the nation of Thundera until Mumm-Ra's return, those who escaped the assault on their kingdom either are with Lion-O or scattered across Third Earth.
There several sub-species of Thunderians, Lions, Tigers, Cheetahs, Panthers, Lynx, and Sabretooths have been seen so far. Lions are considered to be the ruling class.
The acknowledged royalty of the Thunderians. Leo, Claudus, Lion-O, and Lion-O's mother are known parts of this clan.
The Tiger clan was banished by the other Thunderian Clans due to their loyalty to Mumm-Ra and continued worship of the Ancient Spirits of Evil. Tygra was the only representative of the Tiger Clan living in the kingdom of Thundera. In the episode Native Son the ultimate fate of the Tigers and how Tygra came to be a part of the royal family of Thundera is learned. Known representatives of this clan are Tygus, Tygra, Javan, and Caspin
Not much is known of the Cheetah Clan, only member of the clan who is known presently is Cheetara, it is likely they share her super speed trait.
The Panther Clan are considered the warrior class of the Thunderians. Known Panthers are Panthera and Panthro
Not a true clan, and due to the fact that tailed cats have no true connection to a clan they live in poverty. Wilykit and Wilykat are representatives of tailed cats.
Ancient Thunderians (Legacy episode):
Lion-O's Mother (deceased)
Wilytwin's Father (deceased)
(additional note: Snarf is not a Thunderian)