Castlereagh

Castlereagh may refer to:

People

 * Marquess of Londonderry, subsidiary title Viscount Castlereagh, used as courtesy title for the Marquess's eldest son; in particular
 * Robert Stewart, Viscount Castlereagh (1769–1822), later 2nd Marquess of Londonderry: Anglo-Irish statesman and British Foreign Secretary.

Places
In Northern Ireland:
 * Castlereagh (borough), a local government district near Belfast
 * Castlereagh (County Down townland) which gives its name to the borough
 * Castlereagh (County Down barony), latterly divided into
 * Castlereagh Upper and
 * Castlereagh Lower

In the Republic of Ireland:
 * County Mayo: townlands in two baronies:
 * Castlereagh, Clanmorris, Crossboyne parish
 * Castlereagh, Tirawley, Killala parish
 * Castlereagh, County Offaly, townland in Lemanaghan parish, Garrycastle barony
 * County Roscommon:
 * Castlerea, town
 * Castlereagh (County Roscommon barony), around the town
 * Castlereagh (County Roscommon townland), townland around the town
 * Castlereagh, County Waterford, townland in Kilronan parish, Glenahiry barony

In Australia:
 * Castlereagh, New South Wales, a suburb of Sydney
 * Castlereagh River, two rivers
 * Castlereagh Highway, a New South Wales state highway
 * Castlereagh Street, a street in CBD Sydney

Other places:
 * Castlereagh, Nova Scotia, a former village on the Bass River in Nova Scotia, Canada
 * Castlereagh Dam and Reservoir, in Nuwara Eliya district, Sri Lanka

Other uses

 * The Castlereagh (Gilgandra), an early-20th-century newspaper in New South Wales, Australia