This thesis explores interwar town planning in Australia, focusing on the period of large-scale urban expansion in the 1920’s. It problematises aspects of Australia’s urban planning history, particularly the 1920s ‘garden suburb. It also investigates the question of the use of international planning ideas in Australia, and the assertion or creation of authority by the Australian planning movement. The thesis additionally investigates the use of authoritative planning rhetoric for commercial or creative advantage. The thesis argues that the majority of innovative planning projects in the interwar years took place in the formation and foundation of the garden suburb. It shows that the garden suburb – assumed in much planning history to be an inferior form of Ebenezer Howard’s ‘garden city’ ideal – has, in fact, a number of precedents in 19th century Australian suburbia, some of which were retained in 20th century commercial estate design. Much of the Australian town planner’s authority at this time required recognition and awareness of the interests and needs of the general public, as negotiated through land vendors. As Australians looked to the future, and to the US for guidance, they were invited to invest in speculative real estate development modelled on this vision. The thesis concentrates primarily on the lives, careers and work of the British-Australian architect-planner Sir John Sulman; the Chicagoan architect-planners Marion Mahony and Walter Burley Griffin; and the Australian surveyor-planner Saxil Tuxen. These individuals were among the most prominent planners in Australia in the interwar years. All designed Australian garden suburbs, and combined advocacy with practice in private and public spheres. The thesis examines images and personas, both generic and individual, of the planner and the vendor. It shows that the formulation of the garden suburb and design practices, and the incorporation of international elements into Australian planning, are important in the creation of planning practice and forms. It also outlines the way these continue to have significant impact, in diverse and important ways, on both the contemporary built environment and planning history itself.