The Order of Knights of the Hospital of Saint John of Jerusalem, otherwise known as the Knights Hospitaller, was a Mediaeval military order founded in the 12th century. The order came to have a number of bases, called preceptories, in Ireland, one of which was located at Kilteel, County Kildare. There seems to be some confusion about when this was established, and by whom: it may have been Gerald FitzMaurice, first Lord of Offaly, who died in 1204, or his son Maurice FitzGerald, the second lord who died in 1257. It must have been an important centre for the order, since three general chapters were held there during the 14th century. However, with the onset of the suppression of religious orders in the 16th century, Kilteel Preceptory was surrendered to the English authorities in 1540 and two years later granted to Thomas Alen, brother of Sir John Alen, Lord Chancellor of Ireland. Thereafter it fell into decay and little now remains of the buildings other than a few truncated stone columns, parts of a former gatehouse and the outline of a substantial enclosure. More impressive are the adjacent ruins of Kilteel Castle.

Kilteel stands on the boundary of the Pale, that area around Dublin which in the later Middle Ages remained under the control of the English government. Famously, in order to provide protection for its inhabitants, in 1429 King Henry VI offered a grant of £10 to every man within the Pale who built a castle over the next ten years. These castles, usually square or rectangular and several storeys high, are commonly known in Ireland as tower houses, and while they were being constructed prior to the king’s grant – and are similar to the Peel Houses found on the border separating England and Scotland – many of them date from the 15th century onwards. Such would appear to be the case with Kilteel Castle, which measures around 26 by 20 feet and rises five storeys to a height of 46 feet. The building is distinguished from many other examples by a curved projecting staircase in one corner and beside this a two-storey gate house with arched entrance. Immediately behind the tower houses is a large rectangular space, now used as a farmyard but perhaps demarcating the former bawn enclosure. An image published in the Dublin Penny Journal in October 1833 shows a two-storied gabled house, perhaps dating from the 17th century, on the other side of the gatehouse. Some of the outer walls of this building survive, sections of which are fronted with slates. 

Like the Knights Hospitallers preceptory, Kilteel Castle passed into the hands of Thomas Alen in the 1540s and his family appear to have remained owners of the property until the second half of the 17th century (although, according to Samuel Lewis’s Topographical Dictionary of Ireland, they were still claiming tithes there in 1837). However, repeated attacks on the building took their toll on its condition. It was raided and burnt by Rory O’More in both 1573 and 1574 but presumably remained in sufficiently good condition for the 11th Earl of Kildare to station 50 horsemen and 100 foot soldiers there in 1580 during the Second Desmond Rebellion. But in the aftermath of the following century’s Confederate Wars, the Civil Survey of 1654-56 could report that the parish of Kilteel contained ‘One Castle…wch in the year 1640 was valued to be worth sixty pounds butt being since ruined is now valued at ffourty pounds.’ In the second half of the 17th century, Kilteel Castle came into the possession of the Earl of Tyrconnell but following his support of James II the property was taken from him and acquired by the Hollow Sword Blade Company before being sold on in turn to Sir William Fownes. His descendants in turn disposed of Kilteel in 1838, by which time the old castle had long since ceased to be used as any kind of residence.