memorial in the town's square: 'In Memory of the Men and Women of the Berehaven Battalion who fought for the
Irish Republic from 1916 to 1923' The Irish name of the town () originally referred to a
MacCarthy dynasty castle which once stood in the area. This should not be confused with
Dunboy Castle – two miles west of the town – which was the seat of the O'Sullivan Beare family.
Donal Cam O'Sullivan Beare, together with other Gaelic lords and with Spanish aid, rebelled against the English Crown. During the
Siege of Dunboy the castle was reduced by the forces of
Elizabeth I in 1602. He then retreated with his followers to Leitrim. O'Sullivan Beare's stance was commemorated in 2002, and there is a plaque in Irish and English on the castle ruins commemorating those who died there. In 1796
Theobald Wolfe Tone and his confederates sailed into Berehaven Harbour in French men o' war. They anchored off Ahabeg – a
townland five miles east of Castletownbere – but the gales were so violent that they could not land. Wolfe Tone fulminated that he was so close to Ireland that he could almost have spat onto the shore – he reflected, "England has not had such an escape since the
Armada" – perhaps an allusion to the fact that adverse winds frustrated England's enemies on both occasions. For his efforts in preparing the local defences against the French,
Richard White, a local landlord, was created
Earl of Bantry and
Viscount Berehaven in 1816. In the 19th and early 20th centuries, Castletownbere and Berehaven Harbour were an important anchorage and naval port for the
Royal Navy. In 1885, the harbour was a testing site for the development of the
Torpedo ram when the warship
HMS Polyphemus undertook a simulated attack on a fleet at anchor off the town. At Furious Pier, beside the golf course, on 14 May 1921 two soldiers were wounded and Privates Hunter, McCullen, Edwards and Chalmers – all of the
King's Own Scottish Borderers – were shot dead by
Irish Republican Army men led by Michael Og O'Sullivan. There was also an engagement between the IRA and
Black and Tan members of the
Royal Irish Constabulary just outside the town that day but no casualties were sustained. Only one Castletownbere man was killed in the
Irish Civil War; John O'Dwyer killed at
Kealkill, County Cork in 1922 and commemorated on the plaque on Wolfe Tone Square in
Bantry. The deep-water harbour was, up to the 19th century, much used by
smugglers.
Castletownbere Lifeboat Station was opened by the
Royal National Lifeboat Institution in 1997. Poorly-located temporary crew facilities were in use for many years but a new building and moorings were brought into use on 19 May 2013 which significantly reduced the time taken for the lifeboat to put to sea. ==Treaty port==