The global threat that ocean acidification poses to marine ecosystems has been recognized by the UN 2030 Agenda under Sustainable Development Goal, Target 14.3: to reduce ocean acidification. The Global Ocean Acidification Observing Network (GOA-ON) is a collaborative international network to detect and understand the drivers of ocean acidification in estuarine-coastal-open ocean environments, the resulting impacts on marine ecosystems, and to make the information available to optimize modelling studies. The Ocean Acidification Research for Sustainability (OARS) programme, endorsed by the 2021–2030 UN Decade of Ocean Science for Sustainable Development, will build on the work of GOA-ON through its seven Decade Action Outcomes. By employing a Theory of Change framework, and with the co-design of science in mind, OARS will develop an implementation plan for each Decade Action Outcome, which will identify the stakeholders and rights-holders, as well as the tools, means, and positive consequences required for their successful delivery. The organizational structure of GOA-ON, with nine regional hubs, will benefit OARS by providing a vital connection between local and global scales. GOA-ON regional hub case-studies illustrate how activities in the past and future, informed by global and regional priorities, support capacity building and the co-design of ocean acidification science.