Loei (Thai: เลย) is one of the most sparsely populated provinces in Thailand, located on the north-east Thailand. Neighboring provinces (from east clockwise) Nong Khai, Udon Thani, Nongbua Lamphu, Khon Kaen, Phetchabun, Phitsanulok. In the north it borders Xaignabouli and the province of Vientiane Laos. Loei is a city surrounded by mountain ranges whose summits are covered by undulating hazy lines, the abundance of various species. The well-known of them Fu Kradueng, Phu Luang and Phu Ruea.

The province of Loei is covered by low mountains, and in the capital of Loei is located in the fertile basin. Loei River which runs through the province is a tributary of the Mekong river. The river forms the northern edge of the border with neighboring Laos. While the temperature of the hot season, around April, may be more than 40 degrees Celsius, the province is the only place in Thailand, who regularly goes below 0 degrees at night during the cold season around December.