Moussa ag Amastan was the Amenokal of the Kel Ahaggar Tuareg from 1903 to his death in 1920 and the principal indigenous interlocutor of Charles de Foucauld's lexicographical and ethnographic work on Tuareg language and culture. He was born around 1867 in the Hoggar massif into the Kel Ghela noble drum-group of the Kel Ahaggar confederation, the lineage from which the Amenokal had been drawn since the seventeenth century.
He succeeded to the Amenokal-ship in 1903 in the immediate aftermath of the French Saharan-pacification engagements at Tit (1902) that had broken Kel Ahaggar military resistance to colonial expansion. His decision in the following year to accept formal French suzerainty over the Hoggar — the so-called Treaty of Tit, although the formal status of the agreement remains debated in the historical literature — established the political framework under which the Hoggar would be administered through the colonial period.
The relationship between Moussa ag Amastan and Charles de Foucauld, established at Foucauld's arrival at Tamanrasset in 1905, structured the four-volume Dictionnaire touareg-français and the broader corpus of Foucauld's published Tuareg material. Moussa was the principal informant of the lexicographical and ethnographic work, and de Foucauld was the principal interlocutor of Moussa's intellectual life across the fifteen years to the priest's killing in 1916.
He governed the Kel Ahaggar through the Senussi-aligned anti-colonial uprising of 1916–1917 and the subsequent political reconfiguration of the central Sahara under formal French Saharan-territorial administration. He died at Tamanrasset on 6 December 1920 and was succeeded by his nephew Akhamouk ag Ihemma. His tomb at Tamanrasset remains a site of continuing Kel Ahaggar memory.