Telomere shortening to a critical length can trigger aging and shorter life spans in mice and humans by a mechanism that involves induction of a persistent DNA damage response at chromosome ends and loss of cellular viability. However, whether telomere length is a universal determinant of species longevity is not known. To determine whether telomere shortening can be a single parameter to predict species longevities, here we measured in parallel the telomere length of a wide variety of species (birds and mammals) with very different life spans and body sizes, including mouse ( Mus musculus ), goat ( Capra hircus ), Audouin’s gull ( Larus audouinii ), reindeer ( Rangifer tarandus ), griffon vulture ( Gyps fulvus ), bottlenose dolphin ( Tursiops truncatus ), American flamingo ( Phoenicopterus ruber ), and Sumatran elephant ( Elephas maximus sumatranus ). We found that the telomere shortening rate, but not the initial telomere length alone, is a powerful predictor of species life span. These results support the notion that critical telomere shortening and the consequent onset of telomeric DNA damage and cellular senescence are a general determinant of species life span.