The 2030 Agenda for Sustainable Development brought the critical challenge of how private capital can support its new goals—the Sustainable Development Goals (SDGs)—to the attention of finance, business and policy actors. Impact finance instruments, which aim to obtain both financial and positive social/environmental returns simultaneously, can serve as effective institutional mechanisms to support the financing of SDGs. Social impact bonds (SIBs) are part of this emerging field. SIBs represent multi-stakeholder partnerships, built on outcome-based contracts, designed to harness private impact-oriented investors, service providers and public entities to address social or environmental problems.