Kailali District (Nepali: कैलाली जिल्ला), a part of Sudurpashchim Province in Terai plain, is one of the 77 districts of Nepal. The district, with Dhangadhi as its district headquarters, covers an area of 3,235 square kilometres (1,249 sq mi) and has a population 911,155 (2021 census) and (775,709 in 2011 census), (616,697 in 2001 census).

Before the reunification of Nepal by Gorkha King Prithvi Narayan Shah, this district was the part of Doti Kingdom. Nepal lost it to the East India Company after the Anglo-Nepalese war (1814-1816) between the then Kingdom of Nepal and the East India Company followed by territorial concessions of Sugauli Treaty. Later on after the treaty of 1860, Nepal recovered this land along with Kanchanpur, Banke and Bardiya.