Lord Castlereagh may refer to:
Lord Castlereagh (1769–1822), Anglo-Irish politician Marquess of Londonderry, courtesy title for heirs to the peerage Lord Castlereagh (painting), an 1809 portrait by Thomas Lawrence Lord Castlereagh (1802 ship), named after the politician Lord Castlereagh (1803 ship), named after the politician
See also Castlereagh, New South Wales, a suburb of Sydney named after the politician