The Rocky Mountain Floristic Region, also known as the Rocky Mountain Floristic Province, is a floristic region within the Holarctic Kingdom in western North America (Canada and the United States) delineated by Armen Takhtajan and Robert F. Thorne. The region extends from Kodiak Island in Alaska to the San Francisco Bay Area and Sierra Nevada in California. The Vancouverian Province comprises the coastal part of the region for its entire length, including the Pacific Coast Ranges, and the Rocky Mountain Province includes the Rocky Mountains and associated ranges. There are no endemic plant families in the region but many endemic genera and species.