The acceptance of Islam by the inhabitants of the Gao Region and the wider Western Sahel had far-reaching effects, socially, politically and economically. However, no systematic study has yet been undertaken of the archaeology of Islam in this region, although numerous detailed studies exist examine Islamization in West Africa. This study seeks to redress this. The traces of past occupation of the Gao Region between ca.AD 900 and 1250 are here examined, with an emphasis upon understanding the beginning, process, and effect of Islamization. New archaeological evidence is provided, and the existing archaeological evidence re-examined, and then integrated with the historical evidence. Islamic archaeology is still too often regarded as a sub-discipline of art history, and it is hoped that this work will go some way to altering these perceptions, at least for the Western Sahel, as well as to integrating its history into that of its wider region.