Denis-Simon de Marquemont

Denis-Simon de Marquemont (; 30 September 1572 – 16 September 1626) was a French cleric who became Archbishop of Lyon in 1612.

Early life De Marquemont was born on 30 September 1572 in Paris, France, where his father worked in the secretariat of the King. He was educated at the University of Paris and the University of Angers and received a doctorate in utroque iure.

Diplomat In 1594 he travelled to Rome as secretary to Jacques Davy Duperron, where with the help of Abbé Arnaud d'Ossat (1536–1604), later Cardinal d'Ossat (1599-1604), they obtained Henry IV's absolution from the status of relapsed heretic. When Duperron left Rome, de Maquemont remained behind, by order of King Henry, as counsellor to the French ambassador to the Holy See. At various times he was appointed acting ambassador and was so effective, the King determined that the regular ambassador should not make any significant decisions without de Marquemont's advice.

In 1617, he was appointed by King Louis XIII charge d'affaires with Pope Paul V, pending the appointment of an ambassador. He returned to France two years later, but was again sent to Rome in 1622 as assistant to the ambassador. This was despite his personal friendship with the order's founder, Francis de Sales.

Also in 1616, priests of Bérulle's Oratory of Jesus moved to the Choir school; and the Carmel of Lyon was founded by Mère Marie de Jésus on the hill of La Croix-Rousse.

De Marquemont was elevated to cardinal on 19 January 1626 and was appointed Cardinal-Priest of the Church of Trinità dei Monti the following month. He died on 16 September of that year.