Achham District a part of Seti Zone, is one of the seventy-five districts of Nepal, a landlocked country of South Asia. The district, with Mangalsen as its district headquarters, covers an area of 1,692 km² and has a population (2011) of 257,477. It is one of the remotest districts of Nepal. It is accessible by automobile from Kathmandu and Nepalgunj via a paved road that runs along the western border of Nepal from Dhangadhi.

Mangalsen, the district headquarters, is eight hours walk from Sanphebagar - a town in Achham sporting a non-functional domestic airport. A seasonal road exists from Sanphebagar to Mangalsen but is often closed during monsoon season. A bridge crosses the Budhi Ganga river in Sanphebagar allowing access during high water, a second bridge over the second river crossing is also under construction. During 2009/2010, the government of Nepal will be constructing a paved road connecting Sanphebagar to Mangalsen. The district is served by two hospitals, the government district hospital in Mangalsen and one recently opened in Bayalpata that is a collaboration between the government and the non-profit organization Nyaya Health.?

The district has the highest rate of HIV cases in Nepal, which they name "Mumbai disease". One single village was found to have 72 positive cases in 2013.