Caisleán Ghráinne

Republic of Ireland, Ireland

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Caisleán Ghráinne, often known in English as Grace O'Malley’s Castle or Kildavnet Castle, is a 15th-century tower house located on Achill Island in County Mayo, Ireland.

It was built around 1429 by the O'Malley clan and later became closely associated with Gráinne Ní Mháille (Grace O'Malley), the famous Irish chieftain and seafarer often called the “Pirate Queen.” The castle occupies a strategic position overlooking Achill Sound, helping to control the important waterway between Clew Bay and Blacksod Bay.

Its four-storey design includes several defensive features typical of medieval Irish tower houses, reflecting its role as both a residence and a stronghold. Today, Caisleán Ghráinne is a protected National Monument and one of the most recognizable historic sites in County Mayo. Its connection to Grace O'Malley and its dramatic coastal setting make it an important symbol of Ireland’s maritime and medieval heritage.