Saint Catherine of Siena, O.P. (March 25, 1347 - April 29, 1380) was a Tertiary (a lay affiliate) of the Dominican Order, and a scholastic philosopher and theologian. She was born into a prosperous urban family, her parents being Giacomo di Benincasa, a cloth-dyer, and Lapa Piagenti, a daughter of a local poet. She was their 23rd child out of 25 (Catherine’s twin sister, the 24th, died at birth).