Exceeding thermal thresholds causes irreversible damage and ultimately loss of leaves. The lowland tropics are among the warmest forested biomes, but little is known about heat tolerance of tropical forest species. We surveyed leaf heat tolerance of sun-exposed leaves from 147 tropical lowland and pre-montane forest species by determining the temperatures at which potential photosystem II efficiency based on chlorophyll a fluorescence started to decrease (T_Crit) and had decreased by 50% (T₅₀). T_Crit averaged 46.7°C (5^th–95^th percentile: 43.5–49.7°C) and T₅₀ averaged 49.9°C (47.8–52.5°C). Heat tolerance partially adjusted to site temperature; T_Crit and T₅₀ decreased with elevation by 0.40°C and 0.26°C per 100m, respectively, while mean annual temperature decreased by 0.63°C per 100m. The phylogenetic signal in heat tolerance was weak, suggesting that heat tolerance is more strongly controlled by environment than by evolutionary legacies. T_Crit increased with the estimated thermal time constant of the leaves, indicating that species with thermally buffered leaves maintain higher heat tolerance. Among lowland species, T₅₀ increased with leaf mass per area, so species with structurally more costly leaves reduce the risk of leaf loss during hot spells. These results provide insight in interspecific variation in heat tolerance at local and regional scales.