The Roman Catholic Diocese of Sacramento is an ecclesiastical territory or particular church of the Roman Catholic Church in the northern California region of the United States. It comprises the counties of Siskiyou, Modoc, Trinity, Shasta, Lassen, Tehama, Plumas, Glenn, Butte, Sierra, Colusa, Sutter, Yuba, Nevada, Yolo, Placer, Solano, Sacramento, El Dorado, and Amador, and is headquartered in Sacramento, California. Also known as the See of Sacramento, it is led by a bishop who pastors the mother church of the diocese, the Cathedral of the Blessed Sacrament. Originally a major part of the defunct Grass Valley Diocese (which included several counties in northern California and Nevada), Pope Leo XIII established the present-day diocese on May 28, 1886.
Today, the See of Sacramento remains a ceremonial suffragan of the ecclesiastical province of the Archdiocese of San Francisco. Its fellow suffragans include the Dioceses of Honolulu, Las Vegas, Oakland, Reno, Salt Lake City, San Jose, Santa Rosa and Stockton.
A diocese, from the Greek term διοίκησις, meaning "administration", is the district under the supervision of a bishop. A diocese is divided into parishes (in the Church of England into benefices and parishes). This structure of church governance is known as episcopal polity. The word diocesan means relating or pertaining to a diocese. It can also be used as a noun meaning the bishop who has the principal supervision of a diocese.
A diocese also may be referred to as a bishopric or episcopal see, though strictly the term episcopal see refers to the domain of ecclesiastical authority officially held by the bishop, and the term bishopric to the post of being bishop.
An archdiocese (or archiepiscopal see or archbishopric) is more significant than a diocese. An archdiocese is presided over by an archbishop whose see may have or have had importance due to size or historical significance. The archbishop may have metropolitan authority over any other suffragan bishops and their dioceses within his ecclesiastical province.