Maximizing the effectiveness of fuel treatments at the landscape scale is a key research and management need given the inability to treat all areas at risk from wildfire, and there is a growing body of scientific literature assessing this need. We synthesized existing scientific literature on landscape-scale fuel treatment effectiveness in North American ecosystems through a systematic literature review. We identified 127 studies that addressed this topic using one of three approaches: simulation modeling, empirical analysis, or case studies. Of these 127 studies, most focused on forested landscapes of the western United States. Together, they generally provided evidence that fuel treatments reduced negative outcomes of wildfire and in some cases promoted beneficial wildfire outcomes, although these effects diminished over time following treatment and were influenced by factors such as weather conditions at the time of fire. The simulation studies showed that fuel treatment extent, size, placement, timing, and prescription influenced the degree of effectiveness. Empirical studies, though limited in scope, provided evidence that fuel treatments were effective at reducing the rate of spread, progression, extent, or severity of actual wildfires both within and outside of treated areas. Case studies documented outcomes of specific wildfire events and contained managers’ evaluations of fuel treatment effectiveness. These case studies shared certain characteristics associated with changing a wildfire outcome, such as recency of treatment implementation, or strategic placement in relation to previous treatments or wildfires, suppression needs/infrastructure, or prevailing winds and topographic firebreaks. Across the three study types, the importance of treating multiple strata to reduce fuels contributing to fire spread and severity was emphasized. Fuel treatments contributed to fire suppression efforts by reducing costs and facilitating suppression activities such as fireline construction. We conclude that existing literature contains useful information that can inform future fuel treatment planning, but that additional research is needed in underrepresented ecosystems and underdeveloped topics including cost-benefit analysis, fuel treatment longevity, and interactions among fuel, topography, and climate that contribute toward influencing fuel treatment effectiveness. There is a need for more empirical studies that evaluate fuel treatments beyond treatment boundaries, simulation studies that examine conditions expected under future climate scenarios, and case studies that document manager experiences and what they view are indicators of effective landscape-scale fuel treatments.