O Brien, Conor (1880–1952), sailor and author, was born Edward Conor Marshall O'Brien on 3 November 1880 in Cahirmoyle, Co. Limerick, the son of Edward William O'Brien, JP, and Julia O'Brien (née Marshall). A grandson of William Smith O'Brien (qv), he had one brother, two sisters, one step-brother, and two step-sisters. The O'Briens of Cahirmoyle were a collateral branch of the barons of Inchiquin and held imperial sympathies.
Usually known as simply Conor O Brien, he was educated at Winchester College, TCD, and Oxford University, and originally qualified to be an architect. He was though too impulsive for such a career. During the late 1900s he developed an interest in Irish nationalism through the influence of the Gaelic League, becoming a fluent Irish-language speaker and chief patron of an Irish-language college in Carrigaholt, Co. Clare. He was nominated as a leader of the Irish Volunteers in Clare, financing and taking part in the plan of Erskine Childers (qv) and Darrell Figgis (qv) to carry 600 rifles from a rendezvous point in the North Sea to Kilcoole, Co. Wicklow on 1 August 1914, using O Brien's yacht, the Kelpie. Shortly thereafter, he enlisted as a lieutenant in the Royal Naval Volunteer Reserve and served throughout the war. Returning to Ireland in 1919, he was appointed inspector of fisheries for the second dáil. A member of the RSAI and of the Kildare Street Club, Dublin, he took little part in politics, but did stand unsuccessfully for the seanad in 1925.
When Kelpie was wrecked off the Scottish coast in 1921, he settled in Baltimore, Co. Cork, and built a new yacht, Saoirse, a 42ft ketch which subsequently became his home. A keen mountaineer as well as sailor (he always performed with bare feet in both activities), he set sail for New Zealand in June 1923 to join a mountaineering trip. Arriving too late, he decided instead to circumnavigate the rest of the globe, returning to Dún Laoghaire exactly two years after he first set sail, and thereby becoming the first Irish person to sail around the world in his own yacht. The achievement led him to be recognised as one of the outstanding seamen of his time. In the meantime he was awarded the Challenge Cup of the Royal Cruising Club for three successive years. He made important oceanographic observations during his voyage and as a result a newly charted shoal was named after him. Thereafter, he published his best-known book, Across three oceans (1926), followed by a briefer account of his involvement in the Kilcoole gun running, From three yachts (1928). While sailing across the world on the Saoirse, he had called in to the Falkland Islands in 1924. This led to a request from the Falkland Islands Company to design and build a new vessel for them which became the Ilen. He sailed the Ilen to the Falklands himself , arriving in January 1927.
He married (1928) a well-known artist, Kathleen Francis (b. 1886), youngest daughter of Sir George Clausen, RA. The couple thereafter moved to Ibiza, where they lived on the Saoirse, until Kathleen's death (1936); there were no children. Relocating to Cornwall, where he lived with his sister, he wrote books on sailing and works of fiction for children. Although too old for active service when war with Germany broke out in 1939, he assisted the British war effort by serving in the Small Ships Pool, which delivered support vessels across the Atlantic and brought food supplies from the US in private yachts. In 1940 he sold Saoirse to the Royal Cornwall Yacht Club; the boat remained in use until 1980, when it was lost off the Jamaican coast. After the war he retired to another sister's home in Foynes, Co. Limerick, where he lived and continued to write books for children until his death on 18 April 1952.
In 1997 the Hunt Museum in Limerick purchased the Ilen and brought it back from the Falklands to Ireland for restoration. A portrait of O Brien by his wife, Kathleen, is held in the NGI.