The Italian Dominican tertiary (i.e., lay associate) Catherine of Siena (1347–1380) ranks among the leading mystics and theologians of the fourteenth century. Raymond of Capua was Catherine’s spiritual advisor and confessor in Siena during the last six years of her life. During that time, Raymond became convinced that Catherine experienced the deepest union with Jesus that a human being could have. He also marveled at her theology, especially her doctrines of God and humanity, and regarded supernatural powers to be at work in her. However, Catherine became heavily involved in ecclesiastical and political disputes, always siding with the Roman bishop and Italian interests, which led those with French interests to oppose her and attempt to discredit her, especially in the years following her death. For these reasons, Raymond felt called to defend Catherine’s legacy and persuade the papacy to enshrine her as a saint. These, then, were his motivations for composing her biography generally and the selection included here specifically.