Against the background of the millennia-long association of Judentum with the lupine (or canine) in Christian and European discourses, this article focuses on metamorphoses of the human into members of the Canidae family by Jewish-identified, German-born writers. Analysis of, first, Heinrich Heine's characterizations of both Shylock (1838) and the consort of “Prinzessin Sabbath” (1851) and, then, Curt Siodmak's scripts for The Wolf Man (1941) finds werewolves and other were-canids mediating Jewish life and death in their respective historically distinct and distinctly hostile situations: a Gentile Europe resisting Jewish integration in the first half of the nineteenth century, and a post-Emancipation Europe increasingly threatening Jewish existence in the first half of the twentieth. Their hybrid constructions of Jew (explicit or implicit) and wolf (or canid cousin) call attention to how the intersection of Jewish and lupine (or canine) stereotypes functions differently. This article argues that Heine rendered the purported Jewish referent of those interpellating identifications indefinite—that is, as both animal and human and neither; as both Jew and Gentile and neither—while Siodmak demonstrated the tragic consequences on individual lives of such oppressive identifications.