The kingdoms of Dadan and Lihyan are among the most prominent ancient Arab kingdoms that arose in northwestern Arabia during the first millennium BC, specifically in al-‘Ula, considered to the capital of these two kingdoms. Interest in those kingdoms has increased significantly since the beginning of this millennium, when fieldwork started in al-‘Ula, specifically in sites such as Dadan, Umm Daraj, Tell Al-Kuthib and others. Despite this increase in interest, two prominent issues about the relationship between Dadan and Lihyan are the confusion regarding whether they were two separate kingdoms or one kingdom with different names, and the origin of the Dadanites and Lihyanites. This article examines these issues through the analysis of the available archaeological evidence.