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.
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.
With the Ottoman conquest of Crete, around 1650?, the residential diocese was suppressed and listed as titular bishopric of Rhithymna (Latin) / Retimo (Italian).
In 1936, the titular see was suppressed, having has had the following incumbents, all of the lowest (episcopal) rank :
This article about a Roman Catholic titular see in Europe is a stub.