The name, Doonbeg, is derived from Dun Beag, meaning, the small fort. The Village grew up around Doonbeg Castle which was built by Philip MacSheeda Mor Mac Con in the 16th century for the Earl of Thomond, Daniel O’Brien. Turlough MacMahon of West Corca Baiscinn took it in 1585. After his death in 1595 at the end of a fierce siege, the castle was surrendered again to the O’Brien’s who, as victors, hanged the entire garrison back to back. O’Brien, a supporter of Queen Elizabeth, received a grant of most of Tadhg Caoch MacMahon’s (heir of Turlough) property, including the castle.
O’Brien, Earl of Thomond, had possession in 1619 when he gave it to James Comyn. Nicholas Strich Fitznicholas of Limerick, also put in a claim for the castle, as Nicholas Strich’s heir, around this time. It was confiscated by the Crown for failure to repay debts in 1688 and sold in 1703.
When T. J. Westropp visited the castle in 1893, it stood 60 feet high with a frontage of 45 feet from west to east and a depth of 33 feet from south to north. By that time it lacked gables, battlements and chimneys. Despite its condition, seven families lived in the tower. In 1907 two families lived there and when Westropp returned a few years later, a man occupied one of the small western rooms. Up to 1930 it was occupied and and one of its occupants was a schoolmaster named Michael Scanlan. Locals used its upper floor with its mossy overgrowth as a picnic spot since it afforded privacy and beautiful views.
In September of 1939, the castle was in a dangerous condition due to the effects of nature and the crumbling of the river bank. Sadly, most of the castle has come down, leaving only the north-western corner standing. There has been no appreciable structural changes in the last 40 years and it remains today a strong link with Ireland’s rich heritage