-   or at greater length the Cathedral of Saint Corentin, Quimper (French: Cathédrale Saint-Corentin de Quimper, Breton: Iliz-veur Sant-Kaourintin), is a Roman Catholic cathedral and national monument of Brittany in France. It is located in the town of Quimper and is the seat of the Diocese of Quimper and Léon. Saint Corentin was its first bishop.

The cathedral is notable in that, unlike other Gothic cathedrals, it slightly bends in the middle to match the contours of its location, and avoid an area that was swampy at the time of the construction. The cathedral was the site of a devastating fire in 1620 when the bell tower was burned and the populace saw a green devil in the flames.

According to legend King Gradlon met Saint Corentin on the mountain Mėnez-Hom and was so impressed by the strength of his religious faith that he invited the hermit to become Bishop of Quimper.

The cathedral replaced an old Roman church which had a chapel attached to it called the "Chapelle de la Victoire" where Alain Canhiart was buried in 1058. It was in 1239 that the first part of the cathedral was built when Bishop Rainaud commissioned the building of the choir, but it was not until the coming of Duke Jean V at the beginning of the 15th century that momentum gathered and the choir was covered with crisscross vaulting. In the same century, the western side of the cathedral and the nave emerged. The French Revolution and the subsequent Terror put paid to further progress, but after the Concordat of 1801, restoration of the cathedral followed as well as some additional construction.

When the cathedral was completed the choir was out of line with the nave, having a slight curve to the left, this to avoid disturbing the older chapel which contained the tomb of Alain Canhiart. Thus the cathedral has an odd shape, and rather imaginatively some have likened the top part of the cathedral's inclination to the left as suggesting Christ's head leaning to the left when he hung on the cross.