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Ecosystem engineers play fundamental ecological roles by modifying habitats in ways that affect a multitude of other species and by creating refugia with novel microclimates. We hypothesize that burrow-creating organisms may facilitate climate change adaptation by providing refugia from extreme and fluctuating temperatures found aboveground. We support this hypothesis by showing that large burrow-dwelling tortoises, Gopherus polyphemus, likely depend upon burrows for thermoregulation. By exploiting the varied thermal conditions within burrows, tortoises avoided lethal temperatures and extreme fluctuations in body temperature, maintained moderate and stable body temperatures on hot days, and maintained relatively warm temperatures overnight. Climate change is predicted to increase maximum air temperatures throughout the geographic range of this species, with impacts most severe in Florida, US, where the range of future conditions could be above that of current maxima. This implies that environmental temperatures will be above lethal thermal limits more often, highlighting the importance of refugia from extreme conditions. Large burrowing animals (e.g. aardvarks, pocket gophers, rabbits, seabirds, tortoises, wombats) are widely distributed globally and could provide similar thermal refugia for countless commensal taxa. Burrows and the animals that create them are in urgent need of conservation, which will help ensure the widespread availability of refugia that offer protection from extreme temperatures under climate change.