The first written mention of the castle appears in 1150. At that time, the Counts of Savoy controlled the fort, as well as the path between the lake and the mountains.
From the 13th century onwards, the castle was extended, and under Pierre II of Savoy, it became the summer residence of the Counts.
As early as 1150, the Counts of Savoy controlled the fort, as well as the path between the lake and the mountains, which gave them a strategic location on the route leading from the north to the south.
In the 13th century, the Counts furthered their conquests of the territory of Vaud until their domination was extended over approximately two-thirds of the territory which makes up today’s French-speaking Switzerland. The Chillon Castle was extended at that time, in particular under Pierre II of Savoy who transformed it into a summer residence for the Counts. The Counts did not live in Chillon year-round as they moved around to govern and stay close to their subjects. Nevertheless, a castellan bailiff stayed in the castle at all seasons to take care of affairs.
Little by little, the Chillon Castle started to be neglected as the court of Savoy favored other castles. But from 1536 on, the Bernese brought the fort back to life.