On the occasion of Prince Albert II’s visit to three towns of the Matignon lands on the 5^th and 6^th july 2012, this article deals with the origins of the links between the Grimaldi family and the Matignons : the princess Louise-Hippolyte’s wedding with Jacques de Matignon in 1715. Then, the author describes the genesis of the prince’s Breton roots. (full text in French)