This paper examines the origins, spread, and practices of professional forestry in Southeast Asia, focusing on key sites in colonial and post-colonial Indonesia, Malaysia and Thailand. Part 1 challenges popular and scholarly accounts of colonial forestry as a set of simplifying practices exported from Europe and applied in the European colonies. We show that professional forestry empires were constituted under colonialism through local politics that were specific to particular colonies and technically uncolonised regions. Local economic and ecological conditions constrained the forms and practices of colonial forestry. Professional forestry became strongly established in some colonies but not others. Part 2, in a forthcoming issue of this journal, will look at the influence on forestry of knowledge and management practices exchanged through professional-scientific networks. We find that while colonial forestry established some management patterns that were extended after the end of colonialism, it was post-colonial organisations such as the FAO that facilitated the construction of forestry as a kind of empire after World War Two. As a sector, forestry became the biggest landholder in the region only after colonialism had ended.