This article argues for the importance of an exploration of sporting interactions in the British world. In addition, it presents the case for the adaptation of borderlands theory to the British world framework. Such study of British world borderlands is capable of more accurately capturing the spatial and regional variety of this British world and, in particular, the nascent national identities of dominions such as Australia. Sport is a particularly apt vehicle for the examination of such issues in an Australian context, since playing to the 'imaginary grandstand' of international spectators has always occupied a central role in the construction of an Australian national identity. This article uses three brief case studies - cricket, swimming, and Australian Rules football - to explore these theoretical claims.