Implementing ecological connectivity conservation in large landscapes requires cutting-edge science combined with consideration of ecological, socioeconomic, and cultural factors that collectively shape the outcomes of conservation efforts. We outline a theory of change (ToC) for connectivity conservation to improve the ecological condition of landscapes and biodiversity and the ecosystem services upon which humans depend. We review connectivity conservation efforts on four continents in large landscapes that span gradients of latitude, fragmentation, biodiversity value, socioeconomic characteristics, and the richness of data used to assess connectivity and target action. We share the substantial but variable progress made in each landscape and outline specific challenges to achieving conservation goals. Opportunities and challenges in public and private sectors can further leverage the potential of large-scale connectivity conservation to reduce isolation and improve gene flow in functional landscapes worldwide.