The paper presents a "benchmark" map of forest carbon stocks across three continents, covering 2.5 billion hectares of tropical forests in the early 2000s. The map is crucial for developing countries implementing climate change mitigation policies related to reducing emissions from deforestation and degradation (REDD). The study combines data from 4,079 in situ inventory plots and satellite light detection and ranging (Lidar) samples to estimate carbon storage, using optical and microwave imagery to extrapolate over the landscape. The total biomass carbon stock in the study region is estimated at 247 Gt C, with 193 Gt C stored aboveground and 54 Gt C stored belowground in roots. Forests in Latin America, sub-Saharan Africa, and Southeast Asia account for 49%, 25%, and 26% of the total stock, respectively. The uncertainty at the pixel level ranges from ±6% to ±53%, but is constrained at the project (±5%) and national (±1%) scales. The benchmark map provides methodologically comparable estimates of carbon stocks for 75 developing countries, improving upon previous assessments. The map can assist countries in assessing the carbon emissions avoided by implementing policies to reduce deforestation and forest degradation.The paper presents a "benchmark" map of forest carbon stocks across three continents, covering 2.5 billion hectares of tropical forests in the early 2000s. The map is crucial for developing countries implementing climate change mitigation policies related to reducing emissions from deforestation and degradation (REDD). The study combines data from 4,079 in situ inventory plots and satellite light detection and ranging (Lidar) samples to estimate carbon storage, using optical and microwave imagery to extrapolate over the landscape. The total biomass carbon stock in the study region is estimated at 247 Gt C, with 193 Gt C stored aboveground and 54 Gt C stored belowground in roots. Forests in Latin America, sub-Saharan Africa, and Southeast Asia account for 49%, 25%, and 26% of the total stock, respectively. The uncertainty at the pixel level ranges from ±6% to ±53%, but is constrained at the project (±5%) and national (±1%) scales. The benchmark map provides methodologically comparable estimates of carbon stocks for 75 developing countries, improving upon previous assessments. The map can assist countries in assessing the carbon emissions avoided by implementing policies to reduce deforestation and forest degradation.