This chapter draws attention to a familial relationship that has been treated as all but invisible: that between sisters. Although we find examples of this bond in our surviving tragedies, it has long been overshadowed by a focus on male/female relations. This discussion, prompted by the recent productive debate between the fields of classics and political theory over the sisterhood of Antigone, employs close readings of Sophocles’ Tereus and Euripides’ Erechtheus to bring out a feminist interpretation of these texts that places sisterhood front and centre. The chapter shows not only that sisterhood was a more prevalent theme in Greek tragedy than is visible from the extant plays alone, but also that the fragments can be a rich source for scholars working in the area of feminist political theory.