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.

The Proto-Cathedral of St. James the Greater is a church building and parish of the Catholic Church located in Vancouver, Washington, United States. The parish is part of the Archdiocese of Seattle and traces its roots to the initial arrival of missionary priests in the Oregon Country in the 1830s; its first dedicated church building was built in 1846. The church was elevated to a cathedral when the Diocese of Nesqually was established in 1850; the present-day church building was completed in 1885. It was reverted to a parish church when the present-day St. James Cathedral opened in Seattle in 1907. The church building was listed on the Washington Heritage Register in 1986. The church was formally dedicated as a proto-cathedral, i.e., former cathedral, in 2013.