Indigenous fire knowledge offers significant benefits for ecosystem management and human livelihoods, but is threatened worldwide because of disruption of customary practices. In Australia, the historical prevalence and characteristics of Aboriginal burning are intensely debated, including arguments that Aboriginal burning was frequent across the continent. Frequent burning is supported by contemporary Aboriginal knowledge and practice in some regions, but in southern Australia evidence is typically limited to historical and ecological records. Towards characterizing Aboriginal fire regimes in southern Australia, we collaborated with Ngadju people from the globally significant Great Western Woodlands in south-western Australia to document their fire knowledge. We used workshops, site visits, interviews and occupation mapping to aid knowledge sharing. Consistent with the established significance of Aboriginal fire in Australia, planned fires were important in Ngadju daily life and land management. However, Ngadju use of fire was characterized by its selectivity rather than its ubiquity. Specifically, Ngadju described only highly targeted planned burning across extensive eucalypt woodlands and sandplain shrublands. By contrast, frequent planned burning was described for resource-rich landscape elements of more restricted extent (granite outcrop vegetation, grasslands and coastal scrub). Overall, Ngadju fires are likely to have resulted in subtle but purposeful direct effects on the vegetation and biota. However the extent to which they collectively constrained large, intense wildfires remains unclear. Ngadju demonstrated a predictive knowledge of the ecological consequences of burning, including attention to fine-scale needs of target organisms, and application of diverse fire regimes. These are consistent with the recently proposed concept that Aboriginal burning was guided by templates' targeting different resources, although diverse regimes predominantly reflect edaphically driven vegetation patterns rather than template-driven use of fire to create resource diversity. We conclude that Ngadju fire knowledge fills an important gap in understanding Aboriginal fire regimes in southern Australia, highlighting a novel balance between frequent and constrained use of fire.