The former Diocese of Roskilde (Danish: Roskilde Stift) was a Latin Catholic diocese within the Catholic Church that was established in Denmark some time before 1022. The diocese was dissolved with the Reformation of Denmark and replaced by the Protestant Diocese of Zealand in 1537.
Today, the region once within the Diocese of Roskilde's jurisdiction is part of the Roman Catholic Diocese of Copenhagen. Within the Church of Denmark, the region formerly within the ancient Diocese of Roskilde is today divided between the Diocese of Copenhagen, the "new" Diocese of Roskilde, and the Diocese of Helsingør.