Castle Hill is a fairly small yet noticeably steep hill rising from the Northwestern side of Mere in Wiltshire, England. The region is at the Southwestern tip of Salisbury Plain.

As the name suggests, a medieval castle stood on top of the hill for about 200 years. Apparently, the sides of the hill were artificially steepened, and it is generally supposed this was done for defensive reasons, but it is unknown whether this was done in medieval times or earlier, maybe even during the megalithic period. In this respect, Castle Hill may be compared with other unusual hills in Britain, such as Silbury Hill in Wiltshire. Little is known about the castle that once stood on its flattened apex. It's widely believed that stones from the castle were used when building some of the houses in Mere, yet even here there is much evidence to be collected.