This article deals with the office of the Roman Pontiff in the letters from Catherine of Siena to Gregory XI. From her own experience and in a feminine language she reflected on the Petrine primacy bringing together theoretical and practical aspects. In her letters, she highlighted that the papal authority was to serve as a shepherd and cellar keeper of the Blood of Christ. His poor per-formance was an issue that affected the members of the Church. Likewise, she explained to Gregory XI, that the unity of the Church, as the fundamental mis-sion of the Pope, demanded his return to his legitimate see in Rome.