Recent years have seen a sharp increase in the scholarly interest in planning and social engineering, which became widespread in the age of High Modernity. This special issue shows that a belief in (state) planning and in the creation of coherent social orders emerged on the left as well as the right, under democratic and non-democratic regimes alike. Moreover, it argues that a decentred, governance-focused approach to planning, which takes into account not only expert discourses but also practices, forces us to thoroughly reconsider notions of the state, the planning agents as well as the planning recipients. The articles address a series of fundamental questions about social practices, agency and power against the backdrop of the implementation of planning schemes in Europe in the interwar and post-war decades. The case studies cover a wide variety of scales and geographies of planning history, which, taken together, contribute to a richer understanding of planning as a historical and analytical category.