Northeast Thailand or Isan (Isan/Thai: อีสาน, pronounced [ʔīː.sǎːn] ; Lao: ອີສານ, romanized: Īsān; also written as Isaan, Isarn, Issarn, Issan, Esan, or Esarn; from Pāli 𑀇𑀲𑀸𑀦 isāna or Sanskrit ईशान्य īśānya "northeast") consists of 20 provinces in northeastern Thailand. Isan is Thailand's largest region, on the Khorat Plateau, bordered by the Mekong River (along the Laos–Thailand border) to the north and east, by Cambodia to the southeast and the Sankamphaeng Range south of Nakhon Ratchasima. To the west, it is separated from northern and central Thailand by the Phetchabun Mountains. Isan covers 167,718 km (64,756 sq mi), making it about half the size of Germany and roughly the size of England and Wales. The total forest area is 25,203 km (9,731 sq mi) or 15 percent of Isan's area.
Since the beginning of the 20th century, northeastern Thailand has been generally known as Isan, while in official contexts the term phak tawan-ok-chiang-nuea (ภาคตะวันออกเฉียงเหนือ; "northeastern region") may be used. The majority population of the Isan region is ethnically Lao, but distinguish themselves not only from the Lao of Laos but also from the Central Thai by calling themselves khon Isan or Thai Isan in general. But some refer to themselves as simply Lao, and academics have recently been referring to them as Lao Isan or as Thai Lao, with the main issue with self-identification as Lao being stigma associated with the Lao identity in Thai society.