Polar birds and mammals maintain their body temperature despite the extreme challenges of a cold climate. To survive, these animals have evolved a number of anatomical, physiological and behavioural adaptations to cope with low temperature and high rates of heat loss. This talk aims to provide a comparative perspective on thermoregulation in homeothermic endotherms and to highlight how thermal imaging can reveal fascinating insights into how animals cope with the challenges of thermoregulation in the cold. We examine recent studies of the thermal biology of a range of species, including penguins and seals that also demonstrate the importance of behavioural thermoregulation in allowing species to thrive in polar environments.