Blaise Castle is a folly built in 1766 near Henbury in Bristol, England. The castle sits within the Blaise Castle Estate, which also includes Blaise Castle House, a Grade II* listed 18th-century mansion house. The folly castle is also Grade II* listed and ancillary buildings including the orangery and dairy also have listings. Along with Blaise Hamlet, a group of nine small cottages around a green built in 1811 for retired employees, and various subsidiary buildings, the parkland is listed Grade II* on the Register of Historic Parks and Gardens of special historic interest in England.
The site has signs of occupation during the Neolithic, Bronze Age, Iron Age and Roman periods. After the Dissolution of the Monasteries the site was sold. In 1766 Thomas Farr commissioned Robert Mylne to build the sham castle in Gothic Revival style. After Farr's bankruptcy, the estate was sold several times until purchased by John Scandrett Harford, who demolished the previous dwelling in 1789 and built the Neoclassical Blaise Castle House.