ABSTRACT This study presents an integrated, mega-regional, subsurface synthesis of the southeastern Caribbean plate margin that incorporates observations from gravity, seismic refraction, outcrop, and approximately 20,000 line-km of high-resolution 2-D seismic reflection data tied to wells. The primary objective of the study is to better understand the tectonic and basinal transitions from the Lesser Antilles subduction zone (LASZ)—characterized by the subduction of the South American oceanic crust beneath the overriding Caribbean plate and the approximately 300-km (185 mi)-wide, deepwater Barbados accretionary prism (BAP)—to the arcuate, obliquely convergent, and transpressional southeastern Caribbean–South American plate boundary zone—characterized by a complex suite of uplifted provinces, foreland basins, and hybrid sedimentary basins. Early Cretaceous aged allochthonous arc terranes, including the island of Tobago and its offshore component, the Tobago–Barbados Ridge (TBR), were accreted along the deeply buried, lithospheric trace of the LASZ and tectonically transported eastward for hundreds of kilometers along northern South America to their present-day position at the leading eastern edge of the Caribbean plate. Along-strike changes in structures of the BAP are related to progressive phases of deformation that involve thickening of prism strata against the TBR-controlled backstop, frontal accretion that forms the main body of the BAP, horizontal shortening, mud diapirism, rotation and uplift of structures, and backthrusting at the western edge of the prism. The Galera Tear fault zone (GTFZ) formed along the Mesozoic continent–ocean boundary (COB) of the northeastern South American plate. The GTFZ accommodates the differential deformation between provinces of the BAP within the LASZ to the northeast and provinces of the oblique collision and strike-slip zone near Trinidad. Basins affected by subduction-to-strike-slip plate boundary interaction undergo superimposed areas of compressional–transpressional, extensional–transtensional, and strike-slip deformation.