Chiang Mai, sometimes written as Chiengmai or Chiangmai, is the largest city in northern Thailand, the capital of Chiang Mai province and the second largest city in Thailand. It is 700 km (435 mi) north of Bangkok in a mountainous region called the Thai highlands and has a population of approximately 127,000 within the city municipality, as of 2023.

The heart of the city is commonly defined by a square area about 1.6 km x 1.6 km. It is bordered by ancient red brick walls (now only remnants), and has a moat surrounding it.

However, the greater urban area, which includes surrounding districts such as Hang Dong, San Sai, and Saraphi, forms a metropolitan region with an estimated population exceeding 1 million. At the provincial level, Chiang Mai had a projected population of 1.8 million in 2023, according to Thailand's National Statistical Office.

Chiang Mai (meaning "new city" in Thai) was founded in 1296 as the new capital of Lan Na, succeeding the former capital, Chiang Rai. The city's location on the Ping River (a major tributary of the Chao Phraya River) and its proximity to major trading routes contributed to its historic importance.

The city municipality of Chiang Mai (thesaban nakhon) officially only covers parts (40.2 km²) of the Mueang Chiang Mai district in the city centre and has a population of 127,000. This census area dates back to 1983 when Chiang Mai's municipal area was enlarged for the first and last time since becoming the first City Municipality in Thailand (then under Siam) in 1935. The city's sprawl has since extended into several neighboring districts, namely Hang Dong in the south, Mae Rim in the north, Suthep in the west and San Kamphaeng in the east, forming the Chiang Mai urban area with over a million residents.

The city municipality is subdivided into four khwaeng (electoral wards): Nakhon Ping, Sriwichai, Mengrai, and Kawila. The first three are on the west bank of the Ping River, and Kawila is on the east bank. Nakhon Ping District includes the northern part of the city. Sriwichai, Mengrai, and Kawila consist of the western, southern, and eastern parts, respectively. The city center—within the city walls—is mostly within Sriwichai ward.

Mangrai founded Chiang Mai in 1294 or 1296 on a site that the Lawa people called Wiang Nopburi.

The city succeeded Chiang Rai as the capital of Lan Na. Pha Yu enlarged and fortified it and built Wat Phra Singh in honor of his father, Kham Fu. With the decline of Lan Na, Chiang Mai lost importance and was occupied by the Taungoo in 1556. It formally became part of the Thonburi Kingdom in 1774, by an agreement with Chao Kavila, after the Thonburi king Taksin helped drive out the Taungoo Bamar. Subsequent Taungoo counterattacks led to Chiang Mai's abandonment between 1776 and 1791;