This is an interdisciplinary study that aims to reassess Dante's use of Franciscan sources in the Divine Comedy. Particularly, I focus on two important, yet marginalized, theologians: the Provençal friar Pietro di Giovanni Olivi, and his disciple, Ubertino da Casale. Both are coeval of Dante Alighieri, and served as lectores in Florence. In particular, I examine the eschatological aspects of their works, in an attempt to understand how they contribute to Dante's own eschatological vision. Ubertino and Olivi were extremely interested in understanding history through the dense symbolism of the Apocalypse. Therefore, I inspected their works, particularly Olivi's Lectura Super Apocalipsim (a commentary on the Apocalypse written in 1298, of which there exist no modern editions), and Ubertino's Arbor Vitae Crucifixae Jesu, "The Tree of the Crucified Life of Jesus," a massive work on the life of Christ, composed in 1305, in which the author incorporates and develops large parts of Olivi's commentary. I attempt to disentangle the crossed references that link these two books with Dante's Divine Comedy. I aim to revise our knowledge of Dante's appropriation of these sources, for I believe that scholars have unjustly dismissed Ubertino as an unoriginal mediator, on the ground of his ideological dependence on Olivi. Therefore I propose an amendment in Ubertino's favor. Upon a redefinition of Dante's ideological genealogy, I hope to improve our comprehension of how Dante incorporates the eschatology debate of his time in the sacred poem.