This thesis discusses the architecture of early Islamic Iran (16-450/637-1059). To better understand the architectural history of this period, it is necessary to specify in detail how it took shape and to describe its features. Hitherto, no fully comprehensive study has been carried out on this subject. Most of the earlier attempts in that direction are the products of Western scholars. Few of these can be regarded as fully comprehensive - however worthy they were in their own time - in the light of the huge amounts of information now available. This mass of new material, a good deal of it unearthed in the decades since the Islamic Revolution, at last makes it possible to outline in detail the architectural characteristics of this early period. The proposed study will build on the work done by earlier scholars in the field, both western and Iranian, among which two lengthy studies are of particular value. Mehrdad Shokoohy in his unpublished Ph. D. thesis, Studies in the early mediaeval architecture of Iran and Afghanistan (Edinburgh, 1978), describes twelve buildings in 2 Iran and Afghanistan which he dates to the early mediaeval period. This research - some of which has been published in article form1- introduces some monuments that are little known, but there is still ample room for more detailed conclusions and analysis to clarify the evolution of Iranian architecture in this period. The latest study, Frühe Iranische Moscheen (Berlin, 1994), has been carried out by Barbara Finster. This book explains the different types of early mosques in Iran, with much material from literary sources to supplement the author’s own fieldwork. Since the Islamic revolution in Iran (1357/1979), Iranian specialists have carried out some significant architectural and archaeological research; some of this work has not been published yet while other work has been published only in Persian and is difficult of access. In the course of restoration operations in key historical monuments much new and important material has been assembled, though much of this has not been reported yet. To gather together and to order all of this new information is one of the most important aims of my study. Its primary aim is to understand the characteristics and the underlying principles of early Islamic Iranian architecture. In what follows, I shall try to explain how and why this early (and neglected) period holds the key to understanding the Islamic architecture of Iran. It is essentially a transitional period, a time of laying the foundations for what was to come. It documents the earlier experiments in building types, structural techniques and architectural decoration. We see here the earliest attempt of Islamic architecture in Iran to find a distinctive voice. Only few buildings survive – thought it is very likely that more will be 3 found in years to come - but their wide range of form, style, material and decoration reveals a national tradition that – even thought it was still in the process of tradition that was already, in key ways, different from that of the other Islamic lands. The thesis tries to explain how the heritage of pre-Islamic Iranian architecture evolved and how it laid the foundations for Iranian, and especially Saljuq, architecture. Thus, to create a solid base for studying the later period is an important supplementary aim of this thesis.