Michelangelo made this highly finished drawing at the request of Vittoria Colonna, among the most accomplished women of the Renaissance. The widowed marchesa of Pescara, admired for her learning, piety, and eloquence, was active in religious circles and published acclaimed spiritual poetry. When they met about 1536, she became one of Michelangelo’s few intimate friends, and the only woman among them. He too was a poet, and the pair exchanged verses and letters, which joined with the designs he gave her in a heartfelt dialogue about their mutual enthusiasms for church reform and the arts.
Source: James M. Saslow, "Pietà," in Eye of the Beholder, edited by Alan Chong et al. (Boston: ISGM and Beacon Press, 2003): 81