Château de Châtillon-sur-Chalaronne, Medieval castle ruins in Châtillon-sur-Chalaronne, France.

Château de Châtillon-sur-Chalaronne is a ruined castle on a slope above the Chalaronne, south of the town. Its surviving parts are stretches of wall and brick flanking towers; a tall cylindrical brick tower with a broken top stands at one end of a jagged curtain wall pierced by small openings. The site was razed in 1600, and rehabilitation work raised four of the original seven towers.

The fortress was built around 1000 by the Lords of Châtillon as a strategic military post in the region. In 1272 it passed to the Counts of Savoy, and in 1600 it suffered destruction that left it in its present ruined state.

The castle grounds host summer events featuring historical performances that showcase medieval traditions and regional heritage for visitors.

A walking path circles the ruins and provides easy access to view all remaining structures from different angles. The site is open to visitors year-round with clear access points around the perimeter.

In the 14th century the castle captain kept "two large dogs" to serve as lookouts in place of a human watch, according to the records. The site is also linked to Saint Étienne de Châtillon, born here around 1155, who became a Carthusian monk and Bishop of Die.