Invasion by non-native plant species is one of the greatest threats to prairie, savanna, and oak woodland habitats of the Willamette Valley-Puget Trough-Georgia Basin (WPG) ecoregion. Invasive plants can modify the diversity, structure, and function of natural habitats. Effects from non-native invasions have contributed to the decline of many native species found on Pacific Northwest prairie and oak habitats. Even with aggressive management, these unique habitats are severely impacted by nonnative plant invasions. Without management, native species diversity will continue to decline rapidly. Here we provide a list of invasive plants that have extensive detrimental impacts on prairies, savannas, and oak woodlands throughout the ecoregion as a resource for land managers. We provide technical descriptions for the most highly invasive shrubs, grasses, and forbs, current best management practices, and an outlook for the future. When available, we document results from experimental trials. Much of the information presented is based on field observations from experienced land managers. Invasive plants will continue to be a management priority in the WPG for the foreseeable future. Working cooperatively from an ecoregional perspective to track occurrence, develop and implement effective management, and monitor progress is the best platform for successful restoration of the prairies, savannas, and oak woodlands in the WPG ecoregion.