Conisbrough Castle is in the town of Conisbrough near Doncaster, Yorkshire, England. The prominent feature of the castle is the 100 ft high circular keep, which is supported by six buttresses. In the mid-1990s, the keep was restored, with a wooden roof and two floors being rebuilt.

Originally recorded in the Domesday book as a large estate, once owned by King Harold, it was given to William de Warenne, by William I after the Battle of Hastings. It is believed he then built a Motte and Bailey castle on the site at about 1070. The present castle keep was built around 1180 by Hamelin de Warenne, a Plantagenet. Inherited by marriage, he spent a lot of his time here. Hamelin seems to have ordered the cylindrical keep to his own design, there being no other example of this type of keep anywhere in the country. The closest designl to the Conisbrough keep is at Mortemer, near Dieppe in France, also held by the Warenne family. The keep at Mortemer could also be the work of Hamelin Plantagenet. The construction of the stone curtain walls of Conisbrough followed soon after the keep, but the layout and the planning of the stone buildings within the bailey may not have been begun until the thirteenth century and may be the work of Hamelin’s son William, earl from 1202 until 1239. Conisbrough ceded to The Crown on the death without issue of John de Warenne, 8th Earl of Surrey in 1347.

Edward III passed the castle on to his youngest son, Edmund Langley, whose mother, Queen Philippa, administered the estate for him while he was still a child. His tenure lasted until 1402, and the majority of the improvements to the accommodation of the inner ward most probably date to this time. Of Edmunds two sons, Edward, Duke of Albemarle, succeeded in 1402 and died in 1415 at Agincourt. His brother, Richard, Earl of Cambridge, had been beheaded for treason earlier in the same year, but the castle now passed to his widow, Maud, who lived at Conisbrough until her death in 1446. The castle then passed to her stepson, Richard Duke of York, who died at the battle of Wakefield in 1460; his son succeeded him and in 1461 became Edward IV. Thus Conisbrough once again became a royal castle and the estate passed to the Crown, a settlement which was fixed in perpetuity in 1495.

A survey carried out in 1537-38 by commissioners of Henry VIII, records that the gates of the castle, both timber and stonework, the bridge, and about 55m or 60 yds of walling between the tower and the gate had all fallen. In addition, one floor of the keep had fallen in, so that by this date the castle had already reached something like its present state of ruin. It is because of this early ruination, and because of sympathetic ownership thereafter, that the castle still survives with its keep largely intact. During the Civil War of the seventeenth century, many castles were severely damaged either by bombardment during a siege or deliberate destruction afterwards (called slighting), to prevent their further defensive use. However, because the collapse of the gate and a stretch of its defences had already made Conisbrough indefensible, it escaped further destruction at this time.