Olivier de Clisson (1326 – 23 April 1407), nicknamed "The Butcher", was a Breton soldier, the son of the Olivier de Clisson who was put to death in 1343 on the suspicion of having wished to give up Nantes to the English.
He was brought up in England, where his mother, Jeanne de Belleville, had married her second husband. On his return to Brittany he took arms on the side of John de Montfort, who was supported by the English. Olivier distinguished himself at the Battle of Auray (1364), where he lost an eye in the fighting, and earned the nickname "Butcher" because his troops were ordered to take no prisoners. Later, due to differences with de Montfort, Olivier went over to the side of Montfort's rivals, and therefore, France.
In 1370 he joined Bertrand du Guesclin, who had lately become constable of France, and followed him in all his campaigns against the English, including the Siege of Brest in 1373. On the death of du Guesclin, Clisson received the constable's sword, and held the office from 1380 to 1392. He fought with the citizens of Ghent, defeating them at Roosebeke (1382), and later commanded the army in Poitou and Flanders (1389), and made an unsuccessful attempt to invade England.
On his return to Paris, in 1392, an attempt was made to assassinate him by Pierre de Craon, allegedly at the instigation of John V, Duke of Brittany. In order to punish the latter, Charles VI, accompanied by the constable, marched on Brittany, but it was on this expedition that the king was seized with madness. The uncles of Charles VI took proceedings against Clisson, so that he had to take refuge in Brittany.
He was reconciled with John V, and after the duke's death, in 1399, he became protector of the duchy, and guardian of the young princes. He had gathered vast wealth before his death.