Australia is a land of diverse geographical and biological features. The natural features of our coasts are some of the most iconic in Australia—many of the ‘jewels in the crown’ of Australia’s World Heritage properties are in the coastal zone. ‘Coastal zone’ has been defined in various ways in the past. In this chapter, coasts are considered loosely to be the zone of interface between terrestrial, aquatic and marine environments. The size of that interface is different for different issues and processes.