Sainyabuli (Lao ໄຊຍະບູລີ; French: Xaignabouli; alternate spellings: Xaignabouri, Xayaboury, Sayabouli, Sayabouri) is a province of Laos, located in the northwest of the country. Sainyabuli Province covers an area of 16,389 square kilometres (6,328 sq mi). The province borders Bokeo Province and Oudomxai Province to the north, Luang Prabang Province and Vientiane Province to the east, and (from the south clockwise) the Thai provinces Loei, Phitsanulok, Uttaradit, Nan and Phayao. Sainyabuli is the only Laotian province that is completely to the west of the Mekong River (Champasak province also has several districts located west of the Mekong river including Mounlapamok, Soukama and Phontong districts). The province is quite mountainous with the Luang Prabang Range running roughly in a north-south direction and forming a natural border with the Thai highlands. Sainyabuli town is the capital of the province.