The British built about fifty Martello towers around the Irish coastline, especially along the east coast, from Millmount(Drogheda), to Bray, around Dublin Bay but also around Cork Harbour on the south coast. On the east coast, concentrated mainly around Dublin Bay, the towers were in line of sight of each other, providing the ability to communicate with one another, or warn of any incoming attacks. Possibly the most famous is the Martello tower in Sandycove, near Dún Laoghaire, in which James Joyce lived for a few days. Joyce shared the tower with Oliver St. John Gogarty, then a medical student but later to become famous in Irish history as a surgeon, politician and writer. In Ulysses, the fictional character Stephen Dedalus lives in the tower with a medical student, Malachi “Buck” Mulligan, whom Joyce based on Gogarty. The James Joyce Tower, as the tower is now known, houses a museum dedicated to Joyce. A number of other Martello towers are extant nearby at Bullock Harbour, Dalkey Island, Williamstown Seapoint and Sandymount and Martello towers feature in many literary works set in Dublin. During the 1980s, Bono owned the Martello tower in Bray, County Wicklow.
Martello Tower No.7, on Tara Hill, Killiney Bay, is unique, as is its location as an enfilading tower. The Tower is privately owned and has been fully restored, to include a proofed, working King George 3rd Blomefield 18-pounder cannon mounted on a traversing carriage on the crown of the Tower. There is a three-gun battery below the tower, with a glacis. There is also a coach house, artillery store, tool shed, and gunner’s cottage, with resident gunner and gunpowder store. The battery, while restored, remains to be armed and the coach house and artillery store still require some restoration.
On the north side of the city, one can find Martello towers in Portmarnock, Howth, Sutton, Donabate and on both Ireland’s Eye and Lambay Island.
There are seven Martello Towers in the vicinity of Cork Harbour. During the 19th century Fenian uprising, the famous Captain Mackey briefly captured and held the Monning Martello tower near Fota Island in Cork Harbour; this tower is believed to have been the only Martello tower ever captured, other than the original. The other Cork Harbour towers are at Ringaskiddy, Haulbowline Island (now part of the Irish Naval Service HQ) and at Belvelly and Rossleague on the Great Island (near Cobh). There are also Martello towers at Little Island and Rostellan, though these are no longer intact.
The British built two Martello towers on the Hook Peninsula to protect the fort near Duncannon, Co. Wexford and the entrance to Waterford Harbour. There is a third tower on the headland at Baginbun Bay in Co. Wexford.
One of the most interesting Martello towers is in Meelick, Co. Offaly, guarding the river crossing on the River Shannon. As this tower supports three guns (unlike the normal Martello tower which is circular on plan and carries only one gun), it is cam shaped on plan. Currently a rampant growth of ivy covers the tower.
The tower at Seapoint, County Dublin, was formerly the headquarters of the Genealogical Society of Ireland (GSI). The GSI vacated the tower when it found that the atmosphere was not conducive to the preservation of records.
The restored tower at Ilnacullin is a feature of an island garden in Glengarriff, County Cork. Several other towers are still extant, including one at Rathmullan in County Donegal.