The Australian insect fauna is highly endemic and characterised by numerous unique higher-level taxa. In addition, a number of groups are noticeably absent or depauperate on the continent. Many groups found in Australia show characteristic Gondwanan distribution patterns on the southern continents. There are extensive radiations on the plant families Myrtaceae and Mimosaceae, a specialised arid/semiarid fauna, and diverse taxa associated with rainforests and seasonally wet tropical regions. The fauna is also poorly studied, particularly when compared with the flora and vertebrate groups. However, studies in the last two decades have provided a more comprehensive picture of the size of the fauna, relationships, levels of endemism, origins and its evolution. Here we provide an overview of these and other aspects of Australian insect diversity, focusing on six groups, the Thysanoptera and the five megadiverse orders Hemiptera, Coleoptera, Diptera, Lepidoptera and Hymenoptera.