Also known as Kzin, the Kzinti are a race of sentient feline carnivores native to the planet Kzin. Kzinti are highly sexually dimorphic, at least in terms of intelligence; only the males are sentient, a trait that Kzinti sometimes forget that other species (such as humans) do not share. "The Highest of Kzin" is the title bestowed upon the supreme leader of the Kzinti.

The Kzinti are enthusiastic carnivores, and disdain other sentient species, such as Vulcans, that use only plants for sustenance. Since making first contact with Earth humans shortly after Zefram Cochrane's historic first warp flight in 2063, the Kzinti have initiated no fewer than four wars against Earth, but were defeated on each occasion; the last such conflict was concluded in the twenty-first century, and the subsequent human-Kzinti peace was established by the Treaty of Sirius, which remained in force for centuries thereafter, despite occasional incursions by renegade Kzinti, such as the Kzinti attack on the Shuttlecraft Copernicus on stardate 4187.3 (2269).