Abstract: In my book project I introduce a theory explaining how intergovernmental organizations (IGOs) evolve in response to changing member dynamics. I argue that member states create new subsidiary IGOs, which I call linked intergovernmental organizations (LIGOs), in order to “recontract” their cooperation. I evaluate my theory using a multi-method approach, including statistical analyses of original data, quantitative text analysis, and in-depth case studies of LIGO creation at the United Nations and World Bank. This book proposes a major rethinking of processes of reform and evolution at IGOs. The creation of LIGOs provides an avenue to resolve internal disagreements and update IGOs so that they are more reflective of their diverse memberships. This helps maintain (and even expand) cooperation in an increasingly multipolar world.