The medieval prayer Anima Christi (Soul of Christ) is said to have developed from the Eucharistic devotion that St. Thomas Aquinas fostered. This talk presents the prayer and offers a meditation on its first line, "Soul of Christ, sanctify me." Going back to Scripture, early Church teaching, and St. Thomas Aquinas's theology, the presentation will help us be more aware of Christ's soul present in the Eucharist. That soul is extraordinarily filled with grace and truth. In Holy Communion, our souls are united with the soul of our Savior!