Tundra fires may have increased as a result of anthropogenic climate change. To evaluate this hypothesis in the context of natural variability, we reconstructed fire history of the late Quaternary in the Alaskan tundra. Fire-return intervals are spatially variable, ranging from 1648 to 6045 years at our sites. The rarity of historical fires implies that increased fire frequency may greatly alter the structure and function of tundra ecosystems.