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.
Siberians vary from medium to medium-large in size. The formal name of the breed is Siberian Forest Cat, but usually it's simply called the Siberian or Siberian cat. Another formal breed name is the Moscow Semi-Longhair. The cat is an ancient breed that is now believed to be ancestral to all modern long-haired cats. Wikipedia