A series of four wars fought between Earth and the feline Kzinti, all won by the humans, which ended with a treaty that stripped the Kzinti of their warships.
The Earth-Kzin Wars are described in the Animated Series episode The Slaver Weapon. The carnivorous Kzinti attacked humanity four times and lost on every occasion, the last conflict being placed about two hundred years before the 2260s.
The Treaty of Sirius that followed left the Kzinti disarmed, allowed only police vessels. In the episode a Kzinti crew led by Chuft-Captain, officially disowned as pirates, tries to seize an ancient Slaver stasis box weapon in the hope of restoring their people's power, and is thwarted by Spock, Sulu and Uhura.
The Kzinti were created by the novelist Larry Niven. They are mentioned again in Picard, and a Kzinti officer serves aboard the USS Cerritos in Lower Decks.