The Rex rabbit traces to early twentieth-century France, where its defining feature first appeared as a spontaneous genetic mutation. The breed is built around the recessive "rex" coat gene, which shortens the protective guard hairs until they are roughly the same length as the soft undercoat. The result is a uniform, plush pelt with an upright, velvety texture unlike the layered coat of most rabbits.
The mutation is generally credited to a litter of wild-colored gray rabbits noticed in the Loire valley around 1919. French breeders recognized the commercial promise of the dense fur and worked to fix the trait. The new variety was presented to international audiences at the Paris International Rabbit Show in the mid-1920s, where its unusual coat drew considerable attention.
The breed reached North America during the 1920s and was soon taken up by hobbyists and the fur trade alike. Its earliest name, sometimes rendered as "Castorrex," referenced the castor (beaver-like) coloration of the original animals. Selective breeding expanded both the color range and the consistency of the coat over the following decades.
A smaller relative, the Mini Rex, was developed in the United States in the 1980s by crossing the rex coat onto a compact body type. It was recognized by the American Rabbit Breeders Association in 1988 and is considered a distinct breed rather than simply a downsized Rex, though it shares the same signature fur.