Sandro Botticelli created at least five bust-length images of idealized young women that are traditionally identified as Simonetta Vespucci (1453-1476), a Florentine beauty and the platonic love of Giuliano de’ Medici. In this thesis I analyze one of those images, the Allegorical Portrait of a Lady (c. 1480), which is today in the Friedrich Kisters collection in Switzerland. I argue that, while the painting may have begun life as an idealized image of a Florentine beauty, the Kisters Botticelli should be most accurately read as a depiction of the Egyptian goddess Isis. My identification of the subject matter is grounded in references to recent technical analyses of the work, a critical re-assessment of the iconography, and consideration of the social and historical context in which the painting was produced. A 2009 technical analysis of the Kisters painting revealed significant modifications to the image that took place in Botticelli’s workshop. The changes included the incorporation of an elaborate background, the inclusion of a scarf around the neck of the figure, and the exposure of a single, lactating breast. These, I suggest, were completed to shift the identity of the woman from an unknown, idealized woman, or perhaps even Simonetta Vespucci, to the Egyptian goddess Isis. I argue that the iconographic alterations in Botticelli’s painting align the image with ancient texts discussing Isis, such as Plutarch’s De Iside et Osiride (120 C.E.), Apuleius’s Metamorphoses (c. 160-170 C.E.), and the dialogues of Hermes Trismegistus. Finally, I reconstruct possible contexts for the imagery in reference to Renaissance collecting of Egyptian antiquities, Florentine Neoplatonic interest in connections between Isis and the Virgin Mary, and the literary genre of illustrious women. Recognition of the figure as Isis identifies this as one of the earliest known representations of the goddess in the Italian Renaissance and may broaden our understanding of Botticelli’s interest in mythology as well as stimulate new research in field of unidentified, idealized beauties; the Italian Renaissance interest in Egypt; and Botticelli’s workshop.