The Bishopric of Constance, or Prince-Bishopric of Constance, was a Prince-Bishopric and Imperial Estate of the Holy Roman Empire from the mid–12th century until its secularisation in 1802–1803. The much larger Roman Catholic Diocese of Konstanz existed from about 585 until its dissolution in 1821. It belonged to the ecclesiastical province of Mainz since 780/782.