Fermoy (Irish: Mainistir Fhear Maí, meaning 'monastery of the men of the plain') is a town on the River Blackwater in east County Cork, Ireland. As of the 2022 census, the town and environs had a population of approximately 6,700 people. It is located in the historical barony of Condons and Clangibbon, and is in the Dáil constituency of Cork East.

The town's name is of Irish origin and refers to a Cistercian abbey founded in the 13th century. This abbey is believed to have been founded by Domnall Mór Ua Briain, King of Thomond.

The ringfort at Carntierna on top of Corrin hill, 2.4 km (1.5 mi) south of Fermoy, was an important Iron Age site.

A Cistercian abbey was founded in Fermoy in the 13th century. At the dissolution of the monasteries during the Tudor period, the abbey and its lands passed through the following dynasties: Sir Richard Grenville, Robert Boyle and William Forward. However, the site could hardly have been regarded as a town and, by the late 18th century, was little more than a few cabins and an inn.

In 1791, the lands around Fermoy were bought by a Scotsman, John Anderson. He was an entrepreneur who developed the roads and started the mail coach system in Ireland. He designed the town and the streets remain much the same as they were originally built. In 1984, some of his descendants, living in Australia, named a winery, Fermoy Estate, after the town he established. A plaque and bust in his honour were unveiled at the entrance to the town park in 2001.

Fermoy was the site of Fermoy Barracks, a large British Army barracks, when Ireland was under British rule. In 1797, when the army was looking to establish a new and permanent base, Anderson gave them the land as an inducement to locate in Fermoy. Anderson and the town received economic benefit from the arrangement. In 1806 the first permanent barracks, the East Barracks, were built. They were located on 161⁄2 acres of land, and provided accommodation for 112 officers and 1478 men of infantry, and 24 officers, 120 men, and 112 horses of cavalry. A general 130-bed military hospital was also built. In 1809, the West Barracks was built. This also had a 42-bed hospital. When both barracks were complete, there was accommodation for 14 field officers, 169 officers, 2,816 men, and 152 horses. By the 1830s, this was the largest military establishment on the island of Ireland. The town of Fermoy expanded around these facilities and retained its British military facilities until 1922, when the Irish Free State was first established.

During the Irish War of Independence the Irish Republican Army (led by the commandant of the Cork Number Two Brigade Liam Lynch) launched an attack using motor vehicles against a group of off-duty King's Shropshire Light Infantry (KSLI) soldiers on 7 September 1919 as they were attending a Wesleyan Church parade in Fermoy. The IRA killed one soldier (Pte. William Jones from Talog in Wales), wounded four and disarmed the rest of their weapons. After jurors from Fermoy serving on Jones' coroner inquest refused to return a verdict describing his death as a murder, 200 soldiers from the KSLI launched an unofficial reprisal against businesses owned by the jury, looting several drapery and shoe stores.

During the Irish Civil War anti treaty forces were compelled to evacuate Fermoy and burned the barracks and other buildings before retreating into surrounding hills (10 August 1922).