Château de Billy, Medieval castle in Billy, France

Château de Billy is a ruined stone castle on a limestone knoll 14 km north of Vichy, in the Allier. Its main fortification has an ovoid layout; the photographs show pale grey and beige masonry, two round towers on the upper wall, a taller left tower with a small summit window, a wider lower right tower, a shorter square tower at the far left and ruined wall sections at the right. A châtelet guards the entrance.

The fortress was built during the 13th and 14th centuries under Bourbon family control. The French Revolution in 1789 marked the end of aristocratic ownership and changed the castle's purpose.

The castle gave its name to the fortified town and to the châtellenie of Billy, which by the 15th and 16th centuries covered sixty-two parishes and three lordships, the second largest of the seventeen in Bourbonnais. Pierre, bastard of Bourbon, was its best-known châtelain from 1471 to 1488.

The castle is privately owned but open to the public, and it has been listed as a monument historique since 1921. Visitors reach the ruins on foot from the village of Billy, 14 km north of Vichy, and the southern curtain wall has a walkway overlooking the Allier valley.

An elevated walkway within the southern wall offers unobstructed views across the entire Allier Valley. This defensive passage once served both as protection and as a vantage point for observing the broader landscape.