Francis was the eldest of thirteen children of François de Sales, Lord of Boisy. Trained for the law and a public career, he studied at Paris under the Jesuits and at Padua, and at twenty-four refused both the seat in the Savoy senate his father had purchased for him and a brilliant marriage. He was ordained priest in 1593.
His first major mission was to the Chablais — a region of Calvinist Geneva that had been ceded to Catholic Savoy but had remained almost entirely Reformed. With his cousin Louis as sole companion he preached for four years, slept rough, posted his sermons under church doors when no audience would come, and is said to have reconciled some seventy thousand Calvinists to the Catholic Church.
Made Bishop of Geneva in 1602 (he resided at Annecy, since Geneva itself remained Calvinist), he wrote two of the great spiritual classics of Christian devotion: the Introduction to the Devout Life (1608, addressed to ordinary laypeople — the first popular spiritual book of the modern Catholic Church) and the Treatise on the Love of God (1616). With St. Jane Frances de Chantal he founded the Visitation Sisters in 1610. His sermons and 30,000 surviving letters became models of accessible, tender spiritual direction. Pius IX declared him a Doctor in 1877; Pius XI made him patron of writers and journalists in 1923, on the 300th anniversary of his death.