Tortoiseshell cat

Tortoiseshell describes a cat coat colouring found almost exclusively in females, so-called because of the similarity to tortoiseshell material. Male tortoiseshells appear only rarely, and those that do are commonly sterile.

Also called torties for short, tortoiseshell cats combine two colours other than white, either closely mixed or in larger patches. The colours are often described as red and black, but the "red" patches can instead be orange, yellow, or cream, and the "black" can instead be chocolate, grey, tabby, or blue. Tortoiseshell cats with the tabby pattern as one of their colours are sometimes referred to as a torbie.

"Tortoiseshell" is typically reserved for particoloured cats with relatively small or no white markings. Those that are largely white, with tortoiseshell patches, are described as tricolour, as tortoiseshell-and-white (in the United Kingdom), or as calico (in Canada and the United States).

Tortoiseshell markings appear in many different breeds, as well as in non-purebred domestic cats. This pattern is especially preferred in the Japanese Bobtail breed, and exists in the Cornish Rex group.