The Caucasus is a mountain region located at the edge of Europe and Asia, between the Black and Caspian seas. In spite of limited geography and mostly temperate climate, diversity of natural landscapes, plant and animal species, and cultivated plants is unusually high. For these reasons, the Caucasus has been included in the list of global biodiversity hotspots. Proportion of endemic species of higher plants and terrestrial vertebrates varies between 15-30% for individual groups according to different authors, with a vast majority of some taxonomic groups such as terrestrial snails exceeding 80%. There is a number of relict plants and animals, whose relatives are not found in the neighbouring parts of Eurasia, but in the distant regions throughout the northern Hemisphere. Simultaneously, the Caucasus is known as an area of early settlements of hominids and the area of ancient agriculture. High proportion of endemic and relict species is unusual for a continental, non-tropical region. The author describes the biodiversity of the Caucasus region, starting from the Mesozoic time and ending with the current situation, and tries to analyse the evolutionary factors that shaped this diversity.