Mengzi (Chinese: 蒙自; pinyin: Měngzì; former French romanization: Mongtseu; postal: Mengtsz, also Mengtzu) is a city in the southeast of Yunnan province, People's Republic of China. Administratively, it is a county-level city and the seat of the Honghe Hani and Yi Autonomous Prefecture, located about 175 kilometres (109 mi) south-southeast of the provincial capital of Kunming. It is situated in the centre of a fertile valley basin on a plateau 1,000 metres (3,300 ft) above sea level. Mengzi was formerly Mengzi County (蒙自县) until October 2010, when it was upgraded to a county-level city.
The municipal seat is in Wenlan Town.
Located within 30 arc minutes south of the Tropic of Cancer, Mengzi, as with much of southern Yunnan, has a warm humid subtropical climate (Köppen Cwa), with muddled distinction between the seasons and daytime temperatures remaining warm year-round. Highs peak in May before the core of the rainy season and reach a minimum in December; however, the warmest and coolest months are June and December, respectively at 23.2 °C (73.8 °F) and 12.3 °C (54.1 °F); the annual mean is 18.65 °C (65.6 °F). June thru September accounts for over 60% of the annual rainfall of 859 mm (33.8 in) and during this time, some rainfall occurs on a majority of days, resulting in a marked reduction in sunshine. With monthly percent possible sunshine ranging from 34% in June and July to 64% in February, the city receives 2,161 hours of bright sunshine annually.
Yunnan is a province of the People's Republic of China, located in the far southwest of the country. It spans approximately 394,000 square kilometres (152,000 sq mi) and has a population of 45.7 million (2009). The capital of the province is Kunming, formerly also known as Yunnan. The province borders Vietnam, Laos and Burma.
Yunnan is situated in a mountainous area, with high elevations in the northwest and low elevations in the southeast. Most of the population lives in the eastern part of the province. In the west, the altitude can vary from the mountain peaks to river valleys as much as 3,000 metres (9,800 ft). Yunnan is rich in natural resources and has the largest diversity of plant life in China. Of the approximately 30,000 species of higher plants in China, Yunnan has perhaps 17,000 or more. Yunnan's reserves of aluminium, lead, zinc and tin are the largest in China, and there are also major reserves of copper and nickel.
The Han Empire first recorded diplomatic relations with the province at the end of the 2nd century BCE. It became the seat of a Tibeto-Burman-speaking kingdom of Nanzhao in the 8th century CE. Nanzhao was multi-ethnic, but the elite most likely spoke a northern dialect of Yi. The Mongols conquered the region in the 13th century, with local control exercised by warlords until the 1930s. As with other parts of China's southwest, Japanese occupation in the north during World War II forced a migration of majority Han people into the region. Ethnic minorities in Yunnan account for about 34 percent of its total population. Major ethnic groups include Yi, Bai, Hani, Zhuang, Dai and Miao.