Mission San Luis Rey de Francia is a former Spanish mission in an unincorporated part of San Diego County, surrounded by the present-day city of Oceanside, California, United States. The mission was founded on June 13, 1798 by Padre Fermín Lasuén, and was the eighteenth of the Spanish missions established in California. Named for Saint Louis, the mission lent its name to the Luiseño tribe of Mission Indians.