The Siberian is a centuries-old landrace (natural variety) of domestic cat in Russia, and recently developed as a formal breed with standards promulgated the world over since the late-1980s. Since 2006, the breed is recognised for registry and championship status with all major cat registries.

The formal name of the breed is Siberian Forest Cat, but it is typically referred to as the Siberian or Siberian cat. Formerly, sometimes the names Moscow Semi-Longhair and Russian Longhair were also used. The colourpoint variant or sister breed, called the Neva Masquerade, is categorised as a separate cat breed by some registries, including FIFe, WCF, and ACF.

The breed developed from an ancient, natural landrace from Siberia, and is the national cat of Russia. While it began as a landrace, Siberians are selectively bred and pedigreed in all major cat fancier and breeder organisations. This means that all Siberian cats are purebred cats with a formally registered ancestry. It is a medium- to large-sized, muscular breed with a bushy tail.

The Siberian is often called hypoallergenic because it produces less Fel d 1 than other cat breeds. A research study of Siberian cats native to the area of Russia from which the breed stock originated confirmed the subjects produced less Fel d 1 (the strongest among the eight known Fel d 1 allergens produced in cat saliva, which is deposited on their fur when they groom themselves) than non-Siberian cats.

Siberian cats are Russia's native forest cats and are known to have existed for a long time in the dense forests of Siberia. The earliest known reference is from 1000 AD. It was long speculated by cat experts that the ancient breed was the distant ancestor of all modern-day long-haired breeds. However, phylogenetic studies showed that for example Maine Coon cats are descendants of British cats brought to New England by Puritan settlers. It is not relatedness that makes them look similar to the Siberian, but convergent evolution. These breeds all formed in harsh climates in which natural selection pressures for similar qualities. However, Siberians are genetically closely related to Norwegian Forest cats and the random-bred Northern European cat populations.

Outside of Russia, the Siberian cat was first mentioned in the 1864 edition of the German book Brehms Tierleben, where Brehm describes a long-haired cat breed as "a red Tobolsk cat from Siberia" ("eine rote Tobolsker Katze aus Sibirien").

Later in 1889 and 1892, the Siberian cat was again mentioned in the two editions of a book by Harrison Weir, who organised and wrote about some of the earliest cat shows in England in 1871. The Siberian cat is described in the book under its former name, the "Russian Long-haired Cat". However, in the preface of the 1892 edition, Weir also mentions a cat he refers to as a "Siberian Cat":

I have been shown a Siberian Cat, by Mr. Castang, of Leadenhall Market; the breed is entirely new to me. It is a small female Cat of a slaty-blue colour, rather short in body and legs; the head is small and much rounded, while the ears are of medium size. The iris of the eyes is a deep golden colour, which, in contrast to the bluish colour of the fur, makes them to appear still more brilliant; the tail is short and thick, very much so at the base, and suddenly pointed at the tip. It is particularly timid and wild in its nature, and is difficult to approach; but, as Mr. Castang observed, this timidity may be "because it does not understand our language and does not know when it is called or spoken to."