County Cork is the most southwesterly and the largest of the modern counties of Ireland. Cork is nicknamed "The Rebel County" as a result of the support of the townsmen of Cork in 1491 for Perkin Warbeck, a pretender to the throne of England during the Wars of the Roses. In more recent times, the name has referred to the prominent role Cork played in the Irish War of Independence (1919-1921) and its position as an anti-treaty stronghold during the Irish Civil War (1922-23). Attractions include the Blarney Stone and Cobh (formerly Queenstown), the port where many Irish emigrants boarded for their voyage to the United States, Australia, Canada, New Zealand, or South Africa and also the last stop of the Titanic, before departing on its doomed journey. The city of Cork is the second largest city in the Republic of Ireland and capital of the province of Munster.

The remote western area of the county, known as West Cork, is a popular destination for tourists, who visit the small villages and islands including Sherkin Island, Oileán Chléire or Cape Clear Island and Dursey Island. Mizen Head, the "southwesternmost point in Ireland" is also in West Cork, as is Sheep's Head.

In recent years land in the far west of the county has become in high demand internationally, and large numbers of EU citizens have settled in the area, along with celebrities such as Jeremy Irons and director Neil Jordan. West Cork is noted for its rugged natural beauty, fine beaches and distinct social atmosphere.

West Cork has a disproportionately large population of artisans, musicians, poets and playwrights.

Much of what is now county Cork was once part of the Kingdom of Deis Muin (South Munster), anglicised as "Desmond", ruled by the MacCarthy Mor dynasty. After the Norman Invasion in the 12th century, the MacCarthy clan were pushed westward into what is now West Cork and County Kerry. The north and east of Cork were taken by the Hiberno-Norman Fitzgerald dynasty, who became the Earl of Desmond. Cork City was given an English Royal Charter in 1318 and for many centuries was an outpost for Old English culture.

The Fitzgerald Desmond dynasty was destroyed in the Desmond Rebellions of 1569-1573 and 1579-83. Much of county Cork was devastated in the fighting, particularly in the Second Desmond Rebellion. In the aftermath, much of Cork was colonised by English settlers in the Plantation of Munster.

In 1491 Cork played a part in the English Wars of the Roses when Perkin Warbeck, a pretender to the English throne, landed in the city and tried to recruit support for a plot to overthrow Henry VII of England. The mayor of Cork and several important citizens went with Warbeck to England but when the rebellion collapsed they were all captured and executed. Cork's nickname of the 'rebel city' originates in these events. The nickname was later applied to the whole county.

In 1601 the decisive Battle of Kinsale (Irish: Cath Cionn tSáile) took place in County Cork, which was to lead to English domination of Ireland for centuries. Kinsale had been the scene of a landing of Spanish troops to help Irish rebels in the Nine Years War (1594-1603). When this force was defeated, the rebel hopes for victory in the war were all but ended.

County Cork was officially created by a division of the older County Desmond in 1606. In the 19th century, Cork was a centre for the Fenians and for the constitutional nationalism of the Irish Parliamentary Party.

The county was a hotbed of guerrilla activity during the Irish War of Independence 1919-1921. Three Cork Brigades of the Irish Republican Army operated in the county and another in the city. Prominent actions included the Kilmichael Ambush in November 1920 and the Crossbarry Ambush in March 1921. The activity of IRA flying columns, such as the one under Tom Barry in west Cork, was recently popularised in the Ken Loach film The Wind That Shakes The Barley. The centre of Cork city was razed to the ground by the British Black and Tans, in December 1920 as were many other towns and villages around the county.

During the Irish Civil War (1922-23), most of the IRA units in Cork sided against the Anglo-Irish Treaty. From July to August 1922 they held the city and county as part of the so called Munster Republic. However, Cork was taken by troops ofthe Irish Free State in August 1922 in the Irish Free State offensive, that included both overland and seaborne attacks. For the remainder of the war, the county saw sporadic guerrilla fighting until the Anti-Treaty side called a ceasefire and dumped their arms in May 1923.

Michael Collins, a key figure in the War of Independence, was born near Clonakilty and assassinated during the civil war in Béal na Bláth (mouth of flowers in English), both in West Cork.