Castillon-sur-Agen was a medieval castle in the commune of Bon-Encontre, near Agen in Aquitaine, France.
Built on the top of a small hill with sheer rock cliffs[1] (the plateau de Castillou), it was "fortified by both nature and artifice".[2] According to the 12th-century chronicler Robert of Torigny, Henry II of England besieged Castillion-sur-Agen in 1161. After just one week the garrison capitulated.[2] Roger of Howden recorded that nearly 15 years later, in 1175, the site was besieged by Prince Richard (later King Richard I of England), Henry II's son.[3] On this occasion the siege lasted two months; it was part of a campaign of repressing rebellious barons after the Revolt of 1173–1174. It was Richard's first successful siege.[4]
44°12′32″N 0°39′9″E / 44.20889°N 0.65250°E