Holger Carlsen is the protagonist from Poul Anderson's 1961 fantasy novel Three Hearts and Three Lions. Carlsen is an Allied covert operative who assists the Danish Resistance to the Nazis. After an explosion, he finds himself carried to a parallel universe, which proves to have the Matter of France as its historical past. There he finds that the evil of Faerie is encroaching on humanity. His quest finally leads him to discover that he is Ogier the Dane, sent to this universe by Morgan le Fay, and to fight the battle that drives back the evil. After succeeding in this fight, he is thrust back into our world, in which he is able to ensure that the Nazis can not stop a crucial escape of Niels Bohr from occupied Europe.