Cossonay

The lords of Cossonay were one of the oldest seigneurial lineages of the Pays de Vaud, first recorded in 1096 when Ulrich of Cossonay made a donation to the abbey of Romainmôtier. From their castle at Cossonay, west of Lausanne, they held Prangins and Nyon from the late eleventh century.

Humbert I founded the priory of Cossonay. Jean I extended the family lands to Bercher, and his sons split the inheritance between Cossonay and Prangins. The house long opposed the expansion of the counts of Savoy and only submitted gradually.

The male line ended with Louis III and the female line with the heiress Jeanne, who in 1398 granted her town a charter of franchises. On her death in 1406 the succession was disputed, and in 1421 arbitration awarded the lordship to Amédée VIII of Savoy, whose house later raised it to a barony.