Context: Governance is crucial in achieving the success and sustainability of blockchain systems. However, blockchain governance is multi-faceted, complex, dynamic, and challenging due to its decentralized nature and automatically enforced rules and mechanisms. Objectives: This study aims to advance the theory of blockchain governance and support practitioners to deepen the researchers’ and practitioners’ understanding of blockchain governance. Methods: The study is a systematic literature review of 75 articles that applies systems theory to conceptualize blockchain governance as a system and parsimoniously organize its interrelated elements into a conceptual model. Results: The paper proposes a holistic definition and a conceptual model of blockchain governance. Blockchain governance encompasses technical and social means to make decisions on the different levels (e.g., individual, community, organizational, national, international) related to actors, roles, rights, incentives, responsibilities, rules, and the business, technological, legal, and regulatory aspects of a blockchain system during its whole lifecycle. Conclusion: The system-based model of blockchain governance can serve as a reference framework and structured foundation for analyzing, discussing, and developing the governance of blockchain systems.