What is international solidarity and how do we achieve it?International solidarity is a principle and a right, a duty and a mind-set. This chapter grapples with the concept of solidarity, which is a broad and contestable term subject to many meanings and interpretations. Indeed, it is the very malleability of the concept that makes it fertile ground for both this edited volume and a broader conversation among international law’s communities of scholars and policy-makers. Among other possibilities, international solidarity as a principle and a right could address structural inequalities and asymmetries in the international arena. This edited volume has the potential to begin to solidify and concretize the concept of solidarity. To that end, this chapter examines solidarity in the context of global migration, seeking to identify a broad range of solidarity actors and to make the case for an epistemology of solidarity, or solidarity as method.