This article addresses why and how mobility has become central to the EU’s idea of doctoral education, aiming to reconstruct, in a historical perspective, the gradual conceptualisation of mobility as a policy idea. This process began with the discussion of academic mobility in the 1970s, when the European Communities had as yet no responsibility in the field of education, which resulted in the Erasmus Programme. In the late 1990s, the Bologna Process strengthened the discussion, substantially contributing to a consideration of mobility as a policy tool and the establishment of a mobility strategy. In connection with the EU research policy, the integration of doctoral studies into the Bologna Process is specifically analysed. The article concludes with some open questions, including the potentially negative consequences of the instrumentalisation of higher education for the concept of mobility.