The Helmand river, also spelled Helmend, or Helmund, Hirmand, is the longest river in Afghanistan and the primary watershed for the endorheic Sistan Basin. It originates in the Sanglakh Range of the Hindu Kush mountains in the northeastern part of Maidan Wardak Province, where it is separated from the watershed of the Kabul River by the Unai Pass. The Helmand feeds into the Hamun Lake on the border of Afghanistan and Iran.