Oldcastle () is a town in County Meath, Ireland. It is in the northwest of the county, near the border with Cavan, from Kells. The R154 and R195 roads cross in the town's market square. The town is in a townland and civil parish of the same name.

At the 2022 census the town's population was 1,409, a 71% increase from 1996 (when it was 826).

History The area was the birthplace of St Oliver Plunkett, the last Irish Catholic martyr to die in England.

Oldcastle is the 18th-century creation of the Naper family, who had received parts of the Plunkett estate following the Cromwellian wars. St. Oliver Plunkett, who served as Lord Archbishop of Armagh in the seventeenth century, and who was hanged, drawn and quartered at Tyburn in Middlesex (now in the Marble Arch area of the City of Westminster in London) in 1681 on false charges, was the most famous member of this family.

It was also the birthplace of Isaac Jackson, an early Quaker in Ireland, He moved to Ballitore, County Kildare, where he married and raised a large family, mostly all of whom emigrated with their parents to Chester County, Pennsylvania, USA in 1725.

Oldcastle suffered quite badly during the Great Famine and subsequent emigration. Owing to the continuation of a Gaelic way of life in the north of the county, Oldcastle suffered far more than the richer more arable land in the southern part of County Meath. The poorest class lived where Irish culture was strongest and were obliterated by starvation and emigration. Nonetheless, land patterns visible today still reveal a strong attachment to the pastoral farming of Gaelic culture. Politically and culturally the area has a strong tradition of support for radical republicanism, the Gaelic Athletic Association and Comhaltas Ceoltóirí Éireann; a local paper published in the town in the early 1900s gave its name to one of the Irish political parties, Sinn Féin.

Oldcastle Workhouse was located on St. Oliver Plunkett Street (formerly Lennox Street), part of the R195 (the main road to Castlepollard), on the southern edge of the town. Designed by George Wilkinson in a neo-Tudor style and probably built in the late 1830s or early 1840s, it was demolished before the 1950s. Mellow's Park was built by Meath County Council on the site around 1950. Many Germans, Austrians and Hungarians were interned in the old workhouse by the British Government during the First World War.

Fennor Upper and Lower in Oldcastle is said to be named after Queen Medb's daughter, Findabair (Fennor). In Irish Mythology, she was sent as an offering to Cú Chulainn in his fight against Medb and her army from Connacht. She was killed by Cú Chulainn and the area was named after the place where she was murdered and buried.

In 1923, Micheal Grealy, a member of the anti-treaty IRA, robbed two banks – The Hibernian Bank and the Northern Bank – for which he was executed in Mullingar Barracks.

A monument was erected in 1961 in Oldcastle Square by Meath Brigades Executive, Old IRA Federation, 1916–1921 to the memory of Commandant Seamus Coogan and Commandant Patrick McDonnell who were killed by British Crown Forces during the War of Independence. The monument in the form of a cross was unveiled by Seán Dowling, Chairman of the National Federation of the Old IRA.

In November 1997, Michael McKevitt and other IRA dissidents held a meeting in a farmhouse in Oldcastle, County Meath, and a new organisation styling itself Óglaigh na hÉireann was formed.Mooney & O'Toole, pp. 38–39. The organisation attracted disaffected Provisional IRA members from the republican stronghold of South Armagh, as well as other areas including Dublin, Belfast, Limerick, Tipperary, County Louth, County Tyrone and County Monaghan.

Oldcastle detention camp (1916–1918) All of Ireland was part of the United Kingdom of Great Britain and Ireland in 1914 when the First World War broke out. The Alien Restriction Act 1914 was passed on 5 August 1914. The Act introduced strict controls on freedom of movement of foreign nationals and introduced a system of registration with the police. The Act also contained powers to deport foreign nationals and to intern all Austrian and German males between the ages of 17 and 42 (i.e. men of military age). The Oldcastle detention camp was the only permanent civilian POW camp in Ireland, detaining so called “enemy aliens”.The Oldcastle Prisoner of War Camp 1914–1918, John Smith, Riocht Na Midhe – Records of Meath Archaeological and History Society 2010, Vol XX1 This was due to a fear that these men would betray Britain by returning home and joining the German Army or becoming spies in Britain. Not all German and Austrian nationals residing in Ireland were detained immediately. These individuals tended to be citizens who had influential contacts and whose good conduct was guaranteed by them. However, even these men were detained eventually.

After this Act was passed, the British War Office started looking for suitable buildings to convert into detention centres. As stated by John Smith, "disused workhouses were ideal. They had much of the infrastructure to hold hundreds of people: dormitories, kitchens, dining halls, water, washing facilities, an infirmary, store rooms, recreation yards etc". These also had the bonus of being easy to defend with their high walls and being on the outskirts of towns. Oldcastle Workhouse met these requirements perfectly.

In 1838, The Poor Law Act was passed which aimed to relieve the poor/destitute by providing basic food and accommodation. Oldcastle Workhouse was built and opened in 1842 to accommodate 600 people. By 1914 there were only 50 inmates living in the building. After the military approved the conversion of the workhouse into a detention centre, these remaining residents were moved to other workhouses in the area. In November 1914, the building was converted. The eight-foot perimeter walls were reinforced, ‘There are nine sentry boxes around the workhouse grounds, while several galvanized houses have been erected... The grounds are surrounded by barbed wire entanglements about 5 feet high and 14 feet wide.’ Quoted from The Anglo Celt, a newspaper in the area at the time of the camp.

On 12 December 1914, ‘The long expected German prisoners arrived this week in Oldcastle and took up quarters in the disused workhouse.’ This was a headline from the time, The Meath Chronicle on the day of the arrival. The Meath Chronicle reported that via a specially commissioned train 68 German inmates were transported into the town. From there, they were marched through the town under armed guards to their new residence. Two days later, another 26 civilians were moved into the camp. This continued steadily from late 1914 to 1915. 304 inmates were in the camp by February 1915 this number increased to 579 by June 1916. By this time, every space in the workhouse was being utilised by the camp commandant, Major Robert Johnson, including the workhouse's church sacristy. ‘Written accounts show that the highest recorded number of prisoners being held at the Oldcastle Detention Camp was 583 – the building appeared to be operating at full capacity.’ As taken from John Smith's article on the subject. Up to thirty men were housed in a room on regulation camp beds - that is, plank beds with sacks stuffed with straw serving as mattresses Ruth Fleischmann, 'Aloys Fleischmann: Bavarian Musician and Civilian Prisoner of War 1916-1919' in: Oldcastle Camp 1914-1918: An Illustrated History, Ed. Tom French, Meath County Council 2018, 140-1.- one pillow and three blankets per man.

The detainees were civilians from vastly different backgrounds. This ranged from clergymen, jewellery makers and musicians to cooks, butlers and butchers. Though the prison was not entirely pleasant, the inmates had some privileges, especially those who came from a better background. It was possible for the more affluent inmates to buy their own rooms and hire their own servants from among the less affluent detainees. The British wanted to divide the classes as they believed it was not acceptable to put a docker with a doctor. As part of camp life they were allowed to write and send two letters a week containing twenty-four lines. Parcels could be received and visitors were allowed for 15 minutes twice a month. One inmate, Aloys Fleischmann, a Bavarian church musician and composer, wrote to his wife and requested “three blankets and a pillow, a warm knitted Jacket, waterproof boots, a wash bowl, a kettle and mug, cutlery, tobacco and books.” This quote was taken from John Smith's research article. We can gather from this that conditions in the camp were cold, damp and basic. Although it is also reported that if they could gather 100 prisoners they would go on a four-mile march for exercise ending up in a pub in Dromone. They were even allowed to go in and buy a drink. Aloys Fleischmann kept a diary while in the camp.

A journalist visited the camp in June 1915, and he stated that he was “met by a large body of men” and described them as “fine strapping men”’. Account taken from John Smith’s article on the camp. These men caused no trouble for the guards but seemed bored and had nothing to do. The reported goes on to lament that they should be put to better use. Certainly, in the early days, the inmates had nothing to occupy their time so this could have been the reason for four of the detainees to be sent to the mental asylum in Mullingar. By July 1916, it was reported that the detainees had formed committees to run the camp. They took charge of their own washing, drinking water and cooking. There were 3 bakers and 12 cooks among the inmates who provided all the meals for the camp. They were provided with regulation provisions which included "bread, biscuits, fresh or frozen meat, tea, coffee, salt, sugar, condensed milk, fresh vegetables, cheese, butter, peas, beans, lentils and rice". Account taken from John Smith's article on the detention centre. The rest of the men practiced their trades by making toys, jewellery, boots and wood-carving. Many men spent their days painting and sketching. The camp also had two orchestras which gave concerts and played for dramatic performances.

Apart from the boredom one of the other issues for the inmates was the relationships with their families. This led to many divorces and estrangement from their children. There were numerous escape attempts reported in newspapers. One of the most notorious attempts was by Carl Morlang and Aphonsus Grein, who managed to escape for a few days. On the night of 14 August at 9.30 pm the prisoners were noticed missing at roll-call. Morlang and Grein left the prison and made their way northwards to Ballyjamesduff, County Cavan, disguised as two clergymen. ‘At the village of Denn a few miles from Cavan, Grein entered the public house and treated all hands in lavish style.’ An account taken from The Anglo Celt. They were captured the following day by the local constabulary and returned to the camp. When they were searched, they were found to be carrying maps, supplies and money, which they should not have been able to obtain. Also among their belongings it was said there was a letter addressed to Charles Fox thanking him for helping them escape. He was a decorated ex-officer in the British Army and a successful businessman. He was very republican in his views, so he was arrested and tried for treason, which was a hanging offence. However, the charges were dropped. He returned to Oldcastle and was treated like a hero by the locals.