St. Catherine of Siena, a mystic, theologian, and Doctor of the Church, stands as one of the most significant figures in late medieval Christianity. Born in 1347 in Siena, Italy, she entered into the religious life at a young age, joining the Third Order of St. Dominic. Her life was marked by an intense spiritual devotion, an unwavering commitment to reforming the Church, and an extensive body of correspondence that serves as a window into her profound theological reflections. In her letters, St. Catherine combined fervent mystical experiences with a sharp theological mind, seeking to guide both clergy and laity toward a deeper understanding of God's will and the responsibilities of Christian life.

Her letters, which number over 380, are not only historical documents but also theological treatises that reflect the complex spiritual and political realities of the 14th century. Catherine's time was one of considerable turmoil, with the Church facing internal divisions, political power struggles, and external pressures from the burgeoning secular world. In the midst of these struggles, St. Catherine's letters become a lens through which we can better understand both her personal mystical experiences and her contributions to the theological and political debates of her time.