Hybridisation between domesticated animals and their wild counterparts can disrupt adaptive gene combinations, reduce genetic diversity, extinguish wild populations, and change ecosystem function. The dingo is a free-ranging dog that is an iconic apex predator and distributed throughout most of mainland Australia. Dingoes readily hybridise with domestic dogs, and in many Australian jurisdictions distinct management strategies are dictated by hybrid status. Yet, the magnitude and spatial extent of domestic dog-dingo hybridisation is poorly characterised. To address this, we performed a continent-wide analysis of hybridisation throughout Australia based on 24 locus microsatellite DNA genotypes from 3,637 free-ranging dogs. Although 46% of all free-ranging dogs were classified as pure dingoes, all regions exhibited some hybridisation, and the magnitude varied substantially. The south-east of Australia was highly admixed, with 99% of animals being hybrids or feral domestic dogs, whereas only 13% of the animals from remote central Australia were hybrids. Almost all free-ranging dogs had some dingo ancestry, indicating that domestic dogs could have poor survivorship in non-urban Australian environments. Overall, wild pure dingoes remain the dominant predator over most of Australia, but the speed and extent to which hybridisation has occurred in the approximately 220 years since the first introduction of domestic dogs indicates that the process may soon threaten the persistence of pure dingoes. This article is protected by copyright. All rights reserved.