Loei (Thai: เลย, ), is one of the least populated provinces ("changwat") of Thailand. It is in upper northeastern Thailand, also called Isan. Neighboring provinces are (from east clockwise) Nong Khai, Udon Thani, Nongbua Lamphu, Khon Kaen, Phetchabun, Phitsanulok. In the north it borders Xaignabouli and Vientiane Province of Laos.