Saint Giovanni Leonardi (†1609) was an Italian Roman Catholic priest and the founder of the Clerks Regular of the Mother of God of Lucca (Clerici regulari a Mater Dei) a Roman Catholic Religious Order of priests, dedicated to education and pastoral care. He was beatified in 1861 and canonized in 1938 by Pope Pius XI. His liturgical feast is celebrated on 9 October. His relics lie enshrined in Santa Maria in Campitelli, Rome.