Mongkol Borey District (Khmer: ស្រុកមង្គលបុរី) is a district (srok) in the south of Banteay Meanchey Province, in northwestern Cambodia. The district capital is Mongkol Borey town, around nine kilometres south of the provincial capital of Sisophon by road. Mongkol Borey District is the southernmost district of Banteay Meanchey. The district shares a border with Battambang Province to the south. The main railway line from Phnom Penh to Poipet on the border with Thailand runs through the district from north to south.