Castlerea (/ˌkæsəlˈriː/ KASS-əl-REE; Irish: An Caisleán Riabhach, meaning 'brindled castle') is the third largest town in County Roscommon, Ireland.

Clonalis House, located in the west of Castlerea, is the ancestral home of the Clan O'Conor, the last of the High Kings of Ireland.

[2] Castlerea developed under the Sandfords, who established a distillery (at its height producing more than 91,000 litres or 20,000 imperial gallons of whiskey annually), a brewery, and a tannery.

On 11 July 1921, Sergeant James King of the Royal Irish Constabulary was shot in Castlerea on St Patrick Street and died of his wounds shortly afterwards.

The Truce of July 1921 was declared later that day, making Sergeant King the last casualty of the Irish War of Independence.

[3] On 17 June 2020, Detective Garda Colm Horkan was shot dead by a 43-year-old man in Castlerea when his firearm was snatched from him who then fired fifteen rounds at him.

Castlerea's major employers include Supervalu, Harmac Medical Products, Colour Communications Europe, Finola Foods and Lidl.

The demesne is a large public park accessible off Main Street and home to some trees planted by notable figures, including former US ambassador to Ireland Jean Kennedy Smith.