A programme of research on learning in international relations began developing in the 1980s. However, learning research has not realised its potential. This article seeks to stimulate new work on learning by analysing why learning is important in international relations and outlining a research focus that reflects this assessment of learning's significance. The research so far has mostly treated learning as a foreign policy phenomenon, but this fails to capture one of the major reasons for interest in learning. Learning matters in part because of long-standing debates about whether it is possible to make progress in reducing the amount of armed conflict in world politics. For such progress to occur, it is likely that some form of learning would have to take place. However, learning by just a single state will often not be sufficient to change the quality of international outcomes. There thus needs to be research specifically on the possibility of shared learning by two or more states, a research focus this article will label ‘international learning’. A few illustrative examples will demonstrate the feasibility of doing research on shared, cross-national learning.