The origins and dispersals of Austronesian peoples have been widely discussed in Pacific archaeology. There is broad agreement that Taiwan was the primary source for the initial expansion of these human populations in the second half of the third millennium BC. From Taiwan, these Neolithic populations migrated into the Philippines, and then to Indonesia and the Marianas. Rice and pottery disappeared as Austronesians moved further into the Pacific, but agriculture, long-distance voyaging, and an ideology of exploration were widely shared hallmarks of the migration and colonisation. While numerous studies have examined the movement of Austronesian-speaking peoples from Taiwan to the south and east, little attention has so far been given to expansions to the Ryukyu Islands, situated 110320 km northeast of Taiwan. This paper argues that the southern Ryukyu Islands should be included within the Austronesian cultural sphere from the fourth millennium BP until the beginning of the second millennium AD. The prehistory of the southern Ryukyus is important to Austronesian studies because their proximity to Taiwan can help test models of Austronesian origins and early expansions. The southern Ryukyus form part of the northern frontier of settlement in the North Pacific, a frontier that followed a remarkably uniform line between latitudes 2327°N. In the Ryukyus this frontier was maintained despite the existence of further habitable islands only 250 km to the north.