Nakhon Ratchasima (Thai: นครราชสีมา, pronounced [ná(ʔ).kʰɔ̄ːn râːt.t͡ɕʰā.sǐː.māː]) is one of the four major cities of Isan, Thailand, known as the "big four of Isan". The city is commonly known as Korat (โคราช, pronounced [kʰōː.râːt]), a shortened form of its name. It is the governmental seat of the Nakhon Ratchasima province and Mueang Nakhon Ratchasima district. After Bangkok and Chiang Mai, Korat is the third largest city in Thailand.
Korat is at the western edge of the Korat Plateau. Historically, it once marked the boundary between Lao and Siam territory. It is the gateway to the Lao-speaking northeast (Isan). Its location is 14°58.5′N 102°6′E.
As of 2019, the municipal area - as a small part of Mueang Nakhon Ratchasima - had a population of 126,391, while the Mueang Nakhon Ratchasima district, forming Korat's urban area, has a population of 450,000 (Estimate 2022).