Isaac Thomas Hecker (December 18, 1819 – December 22, 1888) was an American Catholic priest and founder of the Paulist Fathers, a North American religious society of men. Hecker was originally ordained a Redemptorist priest in 1849. With the blessing of Pope Pius IX, he founded the Missionary Society of St. Paul the Apostle, now known as the Paulist Fathers, in New York on July 7, 1858. The Society was established to evangelize both believers and non-believers to convert America to the Catholic Church. Hecker sought to evangelize Americans using the popular means of his day, primarily preaching, the public lecture circuit, and the printing press. One of his more enduring publications is The Catholic World, which he created in 1865.