Rebuilt and destroyed more than once, the Château du Plessis-Guériff has stood resilient against the passage of time. A defining moment occurred on 29 January 1471, when Hélène de Bonenfant married Guillaume de Rosnyvinen, forging an alliance between two influential lineages. The name Rosnyvinen would remain tied to the estate until the 19th century.
The family coat of arms — featuring a boar’s head — proudly bears a striking motto: “I attack only when wounded”, accompanied by the battle cry “Defend yourself”. Their timeless maxim, “In all paths, integrity!”, still resonates through the Château’s spirit and legacy.
Over the centuries, the Rosnyvinen family produced eminent military leaders, distinguished magistrates, and gifted scholars, contributing significantly to both Brittany and France. During this flourishing era, the estate expanded well beyond its fortified walls, encompassing nearly 300 properties including manors, farms, tenant holdings, and mills — a testament to its territorial and economic influence.