Ocean acidification (OA) is rapidly emerging as a significant problem for organisms, ecosystems, and human societies. Globally, addressing OA and its impacts requires international agreements to reduce rising atmospheric carbon dioxide concentrations. However, the complex suite of drivers of changing carbonate chemistry in coastal environments also requires regional policy analysis, mitigation, and adaptation responses. In order to fundamentally address the threat of OA, environmental managers need to know where, when, and by how much changes in coastal ocean carbonate chemistry will influence human livelihoods and what they can reasonably do about these effects. Here, we synthesize available biogeochemical and ecological information on the problem of coastal acidification and review actions managers have undertaken thus far. We then describe nine opportunities ripe for decisionmakers to mitigate—and, where necessary, to adapt to—ocean acidification at the spatial scales relevant to their authority.