One of the most influential ideas in Southeast Asian history in recent decades has been Anthony Reid's Age of Commerce thesis, which sees a commercial boom and the emergence of port cities as hubs of commerce over the fifteenth to seventeenth centuries, which in turn spurred political, social and economic changes throughout the region. But how new were the changes described in Reid's Age of Commerce? This paper argues that the four centuries from circa 900 to 1300 CE can be seen as an ‘Early Age of Commerce’ in Southeast Asia. During this period, a number of commercial and financial changes in China, South Asia, the Middle East and within the Southeast Asian region, greatly promoted maritime trade, which induced the emergence of new ports and urban centres, the movement of administrative capitals toward the coast, population expansion, increased maritime links between societies, the expansion of Theravada Buddhism and Islam, increased monetisation, new industries, new forms of consumption and new mercantile organisations. It is thus proposed that the period from 900 to 1300 be considered the Early Age of Commerce in Southeast Asian history.