While early modernists have devoted significant critical attention to the representations of royal authority, like portraits and progresses, that Elizabeth I used to assert political power, a key tool with which the Queen crafted her public image has gone overlooked: her signature. This chapter demonstrates that the “sign manual,” or royal signature, played a crucial role in the construction of queenly authority. Although Henry VII and, to a lesser degree, Henry VIII established the sign manual as a valid authenticating mark, it was in the hands of English queens (Kathryn Parr and Elizabeth) and would-be English queens (Lady Jane Grey and Mary Stuart) that the mark became a widely recognized expression of monarchical power. Drawing on Acts of Parliament regulating the royal signature, literary references to royal signing procedures, and the Tudors’ signatures themselves, this chapter argues that sixteenth-century queens used their signatures to forestall attacks on the legitimacy of their authority. By the end of the century, what was once a little-used administrative mark had become such a highly sought expression of royal favor that Elizabeth assured James VI of Scotland that her word was as good as “my name in parchment, and no less.”