Saint Catherine of Siena (1347–1380) was a Dominican tertiary, mystic, and influential theologian. Born in Siena, Italy, she became known for her deep spiritual insight, extraordinary prayer life, and commitment to serving the poor and sick. Catherine was a strong advocate for the reform of the Church, encouraging the Pope to return to Rome from Avignon, where the papacy had been in exile. Her writings, including The Dialogue, reflect her profound mystical experiences and theological depth. Canonized in 1461 and named a Doctor of the Church in 1970, she is a patron saint of Italy and of Europe.

The Canadian Conference of Catholic Bishops (CCCB) has decreed that this is a Holy Day of Memorial to be observed in Canada.