Abstract: This Working Paper reports on a project led by scientists from in conservation decision appraisal from Queensland University of Technology (QUT) and CSIRO and brings together a group of experts and stakeholders working across the Lake Eyre Basin (LEB). The LEB covers a sixth of Australia, with an array of globally significant natural values that are threatened by invasive plants, among other things. Managers at various levels are investing in attempts to control, contain and eradicate these invasive plant species, under severe time and resources limitations. The Paper provides the first basin-wide assessment of the cost-effectiveness of a range of feasible weed management strategies. The approach brings together expert-derived information on the costs of weed management strategies and their likely biodiversity benefits. Cost-effectiveness is estimated by the likely reduction in invasive species dominance gained per dollar spent on each strategy. The analysis identifies the key invasive plant species to target to protect ecosystem intactness across the bioregions of the LEB, the level of investment required and the extent of ecosystem intactness that may be lost without effective invasive plant species management strategies. The outputs of this work are designed to help guide decision-making and further planning and investment in weed management for the basin.