Louis XIII of France named Vincent de Paul (1580-1660) "Royal Chaplain of the Galleys of France." He continued this work until the last years of his life. This study defines and describes the galleys of his time, reviews the punishment for criminals of condemnation to the galleys. The convicts were moved, mainly from Paris, in a chain gang that terminated in Marseilles. There, the convicts learned the skills of rowing amid squalid and unhealthy conditions. A hospital was founded to care for the sick convicts, and it was served by members of the Congregation of the Mission, founded by Vincent de Paul. The same Missioners also trained candidates for chaplaincies aboard the galleys. The article describes life at sea and reviews the legend of Vincent de Paul charitably substituting for a galley convict. This panoply of works continued long after the saint's death, and developed into a service in favor of European prisoners held for ransom in Tunis and Algiers.