A thick, widespread volcanic ash layer sampled from marine cores in the South Pacific and sub-Antarctic, has been identified using major and rare-earth element chemistry. It is the correlative of the airfall Mount Curl Tephra, the initial eruptive phase of the voluminous Whakamaru Ignimbrite from Taupo, New Zealand. Detailed oxygen-isotope analysis on the late Quaternary section of the core from Deep Sea Drilling Project Site 594, supplemented by other data, places Mount Curl Tephra within the glacial, Isotope Stage 8 and assigns an age of 254+-2 kyr to the tephra. The airfall tephra covers at least 107 km2 with a minimum volume of 700 km3. The Whakamaru Ignimbrite phase encompasses at least another 500-1,000 km3. A combined volume of >1,200 km3 makes this Taupo eruption the largest in the Southern Hemisphere in late Quaternary times. Mount Curl Tephra is so widespread that the eruption possibly caused disruption to the atmosphere and climate, and material from this eruption may be recognizable in sediments 10,000 km from the source.