Marcel Guieysse (1876 -?), Breton nationalist.

He is the son of Pierre-Paul Guieysse, Minister for the Colonies of 1895 with 1896, appointed radical and republican of the Morbihan. In 1925, he is the president of Kengarantez-Vreiz association. In 1936, member eminent of the Breton national Left, it publishes: the Breton Language .

It takes part in the establishment of the Breton National committee with Pontivy at the beginning of July 1940. Near to Olier Mordrel, he is president of the section of the Breton National Parti the Morbihan in October 1940. He flees with the organization Bezen Perrot, in 1944, with his Denise daughter, with the Libération of Rennes. He will be captured and judged in lawsuit in 1946. He assumes the totality of the action of the “Breiz Atao” during the war. Blind man, it is condemned to 5 years of reclusion.