The Helmand river (Pashto/Dari: هیرمند / هلمند; Ancient Greek: Ἐτύμανδρος, Etýmandros; Latin: Erymandrus), also spelled Helmend, or Helmund, Hirmand, is the longest river in Afghanistan and the primary watershed for the endorheic Sistan Basin.

[1] 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.

[2] The word Haetumant is cognate with Sanskrit Setumatī meaning "one which has a dam.

After passing through the city of Lashkargah in Helmand Province, it enters the desert of Dasht-e Margo, and then flows to the Sistan marshes and the Hamun-i-Helmand lake region around Zabol at the Afghan-Iranian border (31°9′N 61°33′E / 31.150°N 61.550°E / 31.150; 61.550).

The Helmand valley region is mentioned by name in the Avesta (Fargard 1:13) as the Aryan land of Haetumant, one of the early centres of the Zoroastrian faith in areas that are now Afghanistan.