This chapter sets out to capture the practical phenomenon of sharing international obligations by developing a concept of shared obligations. In the stipulation of this concept, the chapter draws from and engages with various scenarios in practice that involve obligations incumbent on multiple states or international organizations, including those obligations that have been designated as ‘shared’, ‘joint’ or ‘collective’ in legal literature. By expanding on three elements that characterize a shared obligation, it is argued that the main characteristic that distinguishes obligations that are shared from obligations that are not shared is the existence of a connection between the bearers of an obligation in the performance of that obligation. It is this particular relationship between the bearers of a shared obligation that gives rise to questions regarding performance and international responsibility: who is bound to do what and, subsequently, who can be held responsible for what in case of a breach? All in all, qualifying a particular obligation as ‘shared’ brings such questions to the forefront, and thereby constitutes the first step towards addressing them.