The Archdiocese of Seattle is a Latin Church ecclesiastical territory, or archdiocese, of the Catholic Church in western Washington State in the United States. The Diocese was known as the Diocese of Nesqually from 1850 to 1907. The mother church of the archdiocese is St. James Cathedral in Seattle. The former cathedral is the Proto-Cathedral of St. James the Greater in Vancouver. Its archbishop since 2019 is Paul D. Etienne.

Saint Edward Seminary was an institution for developing Catholic priests in the US state of Washington. Dedicated to Saint Edward the Confessor and located in Kenmore, it operated for 46 years before closing in 1976. The seminary and most of its grounds now constitute Saint Edward State Park. The seminary was located on a 366 acres property purchased in the late 1920s. Building plans were scaled back in 1929 due to the Great Depression. In 1931, the seminary opened as a minor seminary; it became a major seminary in 1935. In 1958, Saint Thomas the Apostle Seminary opened as a major seminary on 50 acres of the site and St. Edward continued as a minor seminary. The Catholic Archdiocese of Seattle closed St. Edward in 1976 and sold it to the State of Washington in 1977. It became Saint Edward State Park in 1978. After St. Thomas closed, Bastyr University leased and later bought that campus.