<p>Ocean-ocean (OO) back-arc basins (BABs) provide natural laboratories for studying lithosphere-asthenosphere interactions, as their formation involves extension of oceanic lithosphere above subduction zones. While individual OO BABs have been studied in detail, a systematic global comparison of their geophysical characteristics is lacking. This study synthesizes datasets including bathymetry, free-air gravity anomalies, heat flow, slab geometry, and seismic tomography to identify first-order patterns across thirteen active and extinct OO BABs. We find that isostatic ratio (IR) effectively captures the degree of lithospheric compensation, distinguishing partially adjusted basins with ongoing extension from extinct basins that are near full equilibrium. Basins such as the North Fiji Basin exhibit complex asymmetries and oblique extension, leading to spatially variable IR values that reveal local tectonic influences beyond slab rollback alone. These findings demonstrate that OO BABs represent a spectrum of extension processes, and that IR provides a robust metric for assessing lithospheric response to tectonic forcing. Integrating global trends with detailed basin-scale analysis advances our understanding of back-arc geodynamics and highlights the need for refined geophysical observations to resolve the interplay of extension, subduction, and mantle dynamics.</p>