This article proposes a research programme devoted to examining 'processes of economization'. In the current instalment we introduce the notion of 'economization', which refers to the assembly and qualification of actions, devices and analytical/practical descriptions as 'economic' by social scientists and market actors. Through an analysis of selected works in anthropology, economics and sociology, we begin by discussing the importance, meaning and framing of economization, as we unravel its trace within a variety of disciplinary backgrounds. We show how in combination, these works have laid the foundations for the study of economization. The second instalment of the article, to appear in the next volume of Economy and Society, presents a preliminary picture of what it might mean to take processes of economization as a topic of empirical investigation. Given the vast terrain of relationships that produce its numerous trajectories, we will illustrate economization by focusing on only one of its modalities - the one that leads to the establishment of economic markets. With emphasis on the increasingly dominant role of materialities and economic knowledges in processes of market-making, we will analyse the extant work in social studies of 'marketization'. Marketization is but one case study of economization.