Yunnan is a landlocked province in the southwest of the People's Republic of China. The province spans approximately 394,000 square kilometres and has a population of 48.3 million. The province borders the Chinese provinces of Guizhou, Sichuan, autonomous regions of Guangxi, and Tibet as well as Southeast Asian countries: Vietnam, Laos, and Myanmar.
Yunnan is China's most diverse province, biologically as well as culturally. The province contains snow-capped mountains and true tropical environments, thus supporting an unusually full spectrum of species and vegetation types. The Yunnan camellia is the provincial emblem.
During summer, the Great Plateau of Tibet acts as a barrier to monsoon winds, trapping moisture in the province. This gives the alpine flora in particular what one source has called a 'lushness found nowhere else'.
This topographic range combined with a tropical moisture sustains extremely high biodiversity and high degrees of endemism, probably the richest botanically in the world's temperate regions. Perhaps 17,000 species of higher plants, of which an estimated 2,500 are endemic, can be found in the province. The province is said to have 'as much flowering plant diversity as the rest of the Northern Hemisphere put together'.
Yunnan has less than 4% of the land of China, yet the province harbors around 42.6% of all protected plant species and 72.5% of all protected wild animals in the country, of which 15% are strictly endemic to Yunnan. Yunnan is home to, most notably, the southeast Asian gaur, a giant forest-dwelling bovine, the Indochinese tiger and the Asian elephant. Other extremely rare species are the Yunnan box turtle and the Yunnan snub-nosed monkey. It is feared that the Yunnan lar gibbon, another moribund species, has already gone extinct. Yunnan province has 11 national and regional nature reserves. In total, the covered protected area in China is about 510,000 hectares.
The freshwater fish fauna is highly diverse with about 620 species, including more than 580 natives, This equals almost 40% of the freshwater fish species in China. Of the Yunnan natives, more than 250 are endemic to the province and many of these are threatened. Several species that are restricted to single lakes are likely already are extinct. By far, the most diverse order in Yunnan are Cypriniformes, both in total species number and number of endemics.
The unique Sinopyrophorus bioluminescent beetles were described from Yunnan in 2019.