West Antarctica has formed the tectonically active margin between East Antarctica and the Pacific Ocean for almost half a billion years, where it has recorded a dynamic history of magmatism, continental growth and fragmentation. Despite the scale and importance of West Antarctica, there has not been an integrated view of the geology and tectonic evolution of the region as a whole. In this Review, we identify three broad physiographic provinces and present their overlapping and interconnected tectonic, magmatic and sedimentary history. The Weddell Sea region, which lays furthest from the subducting margin, was most impacted by the Jurassic initiation of Gondwana break-up. Marie Byrd Land and the West Antarctic rift system developed as a broad Cretaceous to Cenozoic continental rift system, reworking a former convergent margin. Finally, the Antarctic Peninsula and Thurston Island preserve an almost complete magmatic arc system. We conclude by briefly summarizing the geologic history of the West Antarctic system as a whole, how it provides insight into continental margin evolution and what key topics must be addressed by future research.