The Roman Catholic Diocese of Retimo Latin: Dioecesis Rhithymnensis) was a Roman Catholic diocese located in the town of Rethymo (modern day Rethymno) on the north coast of the island of Crete. It was established around 1250 AD. On 5 November 1551, it was renamed as Diocese of Retimo–Ario (Italian) / Rhithymnensis–Ariensis (Latin) and gained territory from the suppressed Roman Catholic Diocese of Ario.