We present a P-wave tomography model of mantle structure under South America, down to ~1800 km depth. DETOX-P1 is a global-scale, multi-frequency inversion of teleseismic P-waves with a particular focus on data sets from South America, where vast areas are only sparsely instrumented. We measured ~ 665,000 cross-correlation traveltimes on 529 broadband stations in South America and on 6,953 stations elsewhere, and closed coverage gaps by adding analyst-picked travel times from the International Seismological Centre. By their locations, depths, and geometries, we distinguish four high-velocity provinces under South America, interpreted as subducted lithosphere (’slabs’). The deepest (~1800-1200 km depth) and shallowest (<600 km) slab provinces are observed beneath the Andean Cordillera near the continent’s west coast. At intermediate depths (1200-900 km, 900-600 km), two slab provinces are observed farther east, under Brazil, Bolivia and Venezuela, with links to the Caribbean. Above 1000 km, slabs are paralleled and underlain on their oceanward flanks by a belt of seismically slow mantle. We interpret the slabs relative to South America’s paleo-position over time, assuming that slabs sank essentially vertically (no more than a few hundred kilometers of lateral displacement). The shallowest slab province carries the geometric imprint of the continental margin and represents ocean-beneath-continent subduction during Cenozoic times. The deepest, far-westerly slab complex formed under intra-oceanic trenches during late Jurassic and Cretaceous times, far west of South America’s paleo-position adjoined to Africa. The two intermediate slab complexes record the gradual transition from intra-oceanic subduction to Cenozoic, “Andean-style” subduction.