Saint Louise de Marillac (†1660) was a French Catholic religious leader and co-founder of the Daughters of Charity. Born near Le Meux, France, she was raised in a noble family but faced early hardships. She married Antoine Le Gras in 1613 and had a son, but after her husband died in 1625, she dedicated herself to religious service. Under the guidance of Saint Vincent de Paul, Louise helped organize charity work for the poor, sick, and orphaned. In 1633, she co-founded the Daughters of Charity, a groundbreaking order where nuns worked actively in society rather than being cloistered. Her leadership and innovative approach to nursing, education, and social work greatly influenced Catholic charitable efforts. She was beatified by Pope Benedict XV in 1920 and canonized on March 11, 1934 by Pope Pius XI. Her feast day is May 9. Her remains are enshrined in the chapel of the motherhouse of the Daughters of Charity at 140 rue du Bac, Paris. She is the patron saint of social workers, and she is honored for her compassion and dedication to serving those in need.