Rabbit hemorrhagic disease virus 2 (Lagovirus GI.2; RHDV2) is a calicivirus that causes necrotising hepatitis with a high case fatality rate in European rabbits (Oryctolagus cuniculus) and various hare (Lepus) species. GI.2 was first detected in France in 2010 and subsequently spread rapidly throughout Europe, causing epidemics in wild and domestic lagomorph populations. GI.2 was first detected in Australia in May 2015, where a closely related lagovirus, GI.1 (originally named RHDV), has been used as a biocontrol agent for more than 20 years. Wild rabbits are a serious environmental and agricultural pest in Australia, and it is currently unclear how the widespread GI.2 will impact ongoing targeted rabbit management operations. Here we describe the initial spread of GI.2 across Australia and its impact on the distribution of GI.1. Within the first 18 months following its detection, GI.2 spread from east to west across the entire continent and became the dominant strain in all mainland states of Australia. Reconstruction of the evolutionary history of 127 Australian GI.2 genome sequences revealed that the virus arrived in Australia at least several months before its initial description and likely circulated unnoticed in wild rabbits in the east of the continent. GI.2 sequences isolated from five hares did not form a monophyletic group but clustered with sequences from sympatric rabbit populations, indicating multiple spillover events from rabbits to hares rather than an adaptation of the Australian GI.2 to a new host species. The spread of GI.2 from what was very likely a single point introduction in New South Wales provides a useful contribution to our understanding of viral spread, evolution, and competition on a continental scale.