Nekomata (猫又, Nekomata) is giant cat who is the boss of the ninja cat underworld.

Appearance: Konoha History Arc - Episode 189 (Filler Arc)

During Sasuke Uchiha's childhood, Itachi Uchiha made a game of collecting paw prints of quick, nimble cats from a normal cat to a lion and the last paw print to be collected was Nekomata's. Itachi once defeated Nekomata and his ninja cats and requested him to fight Sasuke with all his might when he gets older.

(Source: Narutopedia)