Abstract(#br)Citizen participation is essential to create the public value required for sustainable governance. Offline citizen participation enables government policies through physical actions, but is not automatically quantified. Online citizen participation, especially the opinion expression, usually be facilitated by suitable incentives using a recorded participation process, but this makes only limited contribution to governance. The isolation of the processes of two participations limits their mutual promotion. Therefore, using a design science paradigm, we designed an O2O (Offline-to-Online or Online-to-Offline) citizen participation ecosystem for sustainable governance based on social exchange theory. The ecosystem includes three categories of key stakeholders: citizens,... government organizations, and the O2O platform manager. Five components are specified: motivations, contextualized governance policies and strategies, offline/online citizen-to-government contributions, online/offline government-to-citizen rewards, and retention and recommendation. The ecosystem was evaluated and then improved using a case study on O2O green commuting governance in China. This study provides a reproducible framework to combine offline and online citizen participation to enhance collaborative social governance in the digital age.