Abstract: The Yinggehai Basin offers advantages for implementing offshore CCUS, but the basin-scale suitability and storage potential remain insufficiently quantified. This study aims to assess geological suitability, estimate storage capacity, and propose a provincial CCUS planning framework for Hainan. Based on integrated geological, borehole, and seismic datasets, we analyzed formation pressure–temperature conditions, reservoir-caprock assemblages, and depositional facies in the Yinggehai Basin to delineate CO₂ storage-suitable areas and favorable structural targets. Storage potential estimates were combined with Hainan Province CO₂ emissions characteristics to inform offshore CCUS planning recommendations. The Yingdong Slope and the Lingao Uplift meet the temperature–pressure and reservoir-caprock requirements for CO₂ geological storage and are identified as the basin’s secondary structural units most suitable for saline aquifer storage. Their estimated effective storage capacities are 2.13 Gt and 1.06 Gt, respectively. Two favorable structural targets were identified: HK30-3 and LG20-1, with estimated effective storage capacities of 43 Mt and 343 Mt, respectively. Notably, HK30-3 lies at an approximate straight-line distance of only ～100 km from Hainan’s major industrial centers and is therefore suitable as a demonstration target for megaton-to-tens-of-megatons-scale offshore CCUS in Hainan. The Yinggehai Basin possesses the geological conditions required for offshore CO₂ geological storage and exhibits gigaton-scale effective storage capacity. The findings provide a scientific basis for Hainan Province to pursue carbon neutrality and for coastal regions to explore pathways toward net-zero emissions.