Dunguaire Castle (Irish: Dún Guaire) is a 16th-century tower house on the southeastern shore of Galway Bay in County Galway, Ireland, near Kinvarra. The castle's 75-foot tower and its defensive wall have been restored to excellent condition, and the grounds are open to tourists during the summer. It is thought to be the most photographed castle in Ireland.

The castle was built by the Hynes clan in 1520, a family who may have been associated with the area since 662, when the site is believed to have once been the royal palace of Guaire Aidne mac Colmáin, the legendary king of Connacht and progenitor of the clan. Dunguaire Castle was transferred in the 17th century to Oliver Martin, (father of Richard Martin fitz Oliver). It remained in his family until it was purchased in the early 20th century by the surgeon and poet Oliver St. John Gogarty. Gogarty began restoring the castle and established it as the meeting place for the leading figures of the Celtic Revival, such as W.B. Yeats, George Bernard Shaw, Augusta, Lady Gregory, and John Millington Synge.