Arab incursions and raids into Armenia began in approximately 640, but neither concerted effort at conquest nor prolonged Arab presence followed immediately. Arabic and Armenian sources are confusing and present contradictory material for much of the seventh century. With the rise of the local Arab emirates in the late eighth century and the Armenian kingdoms in the ninth, the defining lines between the Islamic world and Armenian controlled land were not always clearly established. As a result, the relationship between Armenia and the Realm of Islam is occasionally unclear in modern scholarship. It has sometimes been assumed that Armenia was a 'thaghr' specifically because it was a borderland that is ethnically, linguistically and religiously different from the caliphate and as such represents a zone between two worlds. This theory cannot possibly withstand closer examination, as it assumes that the caliphate itself was ethnically, linguistically and religiously uniform. This paper considers how Arab geographers in the Abbasid period conceived of Armenia and argues that Armenia, from their perspective, was part of the Realm of Islam. This conclusion is based on specific passages from geographical texts, including discussions on religion, tax reports and use of specific vocabulary (specifically the terms 'hadd' and 'thaghr'). Additionally, this paper draws attention to both internal and external borders of the Islamic world, with particular consideration given to A. Ter Ghewondyan's argument that Ibn Hawqal's division of Armenia reflected the border between Bagratid and Arab lands. The main sources include al-Islakhr?, Ibn Hawqal, al-Muqaddasq, Ibn al-Faq h, Ibn Khurrad dhbih and al-Idrns , while recognizing the discrepancies in how each of these geographers defines the province of Armenia. The goal of this paper is to add Armenian data to the discussion of the frontiers of Islam with the hope of formulating a clearer conception of (1) how Arab geographers understood Armenia and (2) how the example of Armenia can add to a comparative discussion of the frontiers of Islam.