Open Social Innovation Ecosystems (OSIEs) have emerged as a crucial setting for addressing grand challenges through stakeholders’ joint efforts. However, despite their undoubtful benefits, they entail a high level of complexity, given their nature of multi-sided (intended as both multi-stakeholder and cross-sectorial) and many-goal contexts, that increases their coordination costs and alignment needs. As such, they require structuring effective governance mechanisms to engender the anticipated impact. Adopting an ecosystem perspective on Open Social Innovation, we define OSIEs and describe their peculiarities, culminating with categorizing them according to their degree of complexity, namely structural complexity and complementarity intensity. Furthermore, building on the review of the extant literature, we provide a novel typology of contracts that goes beyond their current conceptualization as governance mechanisms and that is applicable to complex multi-stakeholder initiatives like OSIEs. To conclude, through a prescriptive theorizing effort, we offer specific propositions to point out which types of contracts are more effective for different OSIEs. Overall, we aim to provide valuable insights for both theory and practice and increase awareness of tackling grand challenges through OSIEs and contracts as effective governance mechanisms.
