Subduction zones are pivotal for the recycling of Earthtextquoterights outer layer into its interior. However, the conditions under which new subduction zones initiate are enigmatic. Here, we constructed a transdisciplinary database featuring detailed analysis of more than a dozen documented subduction zone initiation events from the last hundred million years. Our initial findings reveal that horizontally forced subduction zone initiation is dominant over the last 100 Ma, and that most initiation events are proximal to pre-existing subduction zones. The SZI Database is expandable to facilitate access to the most current understanding of subduction zone initiation as research progresses, providing a community platform that establishes a common language to sharpen discussion across the Earth Science community. Despite numerous advances in our understanding of subduction since the theory of plate tectonics was established, the mechanisms of subduction zone initiation remain highly controversial. Here, the authors present a transdisciplinary and expandable community database of subduction zone initiation events in the last 100 Ma, which establishes a clear direction for future research.