Early Modern Drama and Terms of Endearment is the first expansive study of pet names in sixteenth and seventeenth century English performance. In this dissertation I look to terms of endearment shared by couples in plays by William Shakespeare, Thomas Dekker, Francis Beaumont, and Margaret Cavendish to explore the performative function of pet names and its relationship with early modern notions of marriage, desire, and gender hierarchy. Ultimately, I argue that intimate language expresses forms of mutuality and solidarity which contest dynamics of power, and that the performative nature of affectionate language affords a better understanding of an addressee's character, the character of the addressor, and, particularly, the relationship between the two.In this dissertation, I approach the theatrical use of affectionate address not merely as a socio-linguist, or even a cultural historian, but from the perspective of an avid theatre-goer and literary scholar. My intention is to magnify etymological details in order to connect to the larger narrative context, consider gender implications, and provide affordances for performance and editorial practices. In this sense, this dissertation rescues terms of endearment from obscurity, revealing them as consequential not only for the negotiation of power hierarchies and the establishment of mutuality, but for modern theatrical and editorial practice.