This Memoir presents and discusses recent research mainly concerning the Permian and Triassic geological development of South Island in its regional context, which includes New Zealand as a whole, the continent of Zealandia, eastern Australia and Antarctica. The Permian and Triassic geology of the South Island encompasses several geological units which shed light on fundamental geological processes. These include a well-developed oceanic volcanic arc, a classic subduction-related ophiolite (oceanic crust on land) and a very thick succession of continental margin forearc sediments. These, and other related geological units, constitute the oldest extensively outcropping basement of Zealandia, which can be considered as the world's seventh largest continent, albeit 94% submerged (Mortimer et al. 2017). The supercontinent, Gondwana, formed during the Late Neoproterozoic and remained until its progressive break-up into crustal fragments during the Mesozoic. During this prolonged period, New Zealand and adjacent crustal units were located along the SE edge of Gondwana. Subduction took place beneath this margin during the Paleozoic–Mesozoic, until the end of Early Cretaceous time ( c. 100 Ma) when it halted, followed by rifting of the Tasman Sea Basin. This volume consists of 14 contributions, comprising a mix of new-data-based papers (and one note) and several review and synthesis papers. The contributions largely concern igneous and sedimentary geology, tectonics and biostratigraphy. Particular emphasis is placed on field geology, petrography and geochemistry. Some aspects are less well covered (e.g. Permian–Triassic geology of New Zealand's Cordilleran-style Median Batholith; metamorphic geology), primarily because there is a large amount of existing and/or recently published data. While the Permian–Triassic terranes bear imprints of Gondwana break-up and Neogene Alpine Fault development, these topics are outside the scope of this volume. The final chapter discusses various tectonic-based interpretations for the Permian–Triassic development of Zealandia and points the way to an overall synthesis. In this introductory …