Neanderthals inhabited Western Eurasia from 350,000 to 40,000 years ago during the Pleistocene. This study uses a spatiotemporal species distribution model, paleoclimate data, and dated Neanderthal sites to estimate the fundamental climatic niche space of Neanderthals. The results show that Neanderthals occupied a relatively narrow niche space, with a larger geographic range than suggested by the material record. The projected potential niche space declined over time, possibly contributing to their extinction. Neanderthals were primarily found in Western Europe, with their range expanding during warmer periods. The study also found that Neanderthal niches were more suitable in warmer, wetter, and more productive environments. The model suggests that Neanderthal populations declined in size and distribution over time, with the projected potential niche space peaking around 121,000 years ago and then gradually decreasing. The study highlights the importance of climate in Neanderthal survival and extinction, as well as the role of human migration in shaping their fate. The findings provide new insights into the spatial and temporal distribution of Neanderthals and the factors influencing their adaptation and extinction.Neanderthals inhabited Western Eurasia from 350,000 to 40,000 years ago during the Pleistocene. This study uses a spatiotemporal species distribution model, paleoclimate data, and dated Neanderthal sites to estimate the fundamental climatic niche space of Neanderthals. The results show that Neanderthals occupied a relatively narrow niche space, with a larger geographic range than suggested by the material record. The projected potential niche space declined over time, possibly contributing to their extinction. Neanderthals were primarily found in Western Europe, with their range expanding during warmer periods. The study also found that Neanderthal niches were more suitable in warmer, wetter, and more productive environments. The model suggests that Neanderthal populations declined in size and distribution over time, with the projected potential niche space peaking around 121,000 years ago and then gradually decreasing. The study highlights the importance of climate in Neanderthal survival and extinction, as well as the role of human migration in shaping their fate. The findings provide new insights into the spatial and temporal distribution of Neanderthals and the factors influencing their adaptation and extinction.