The O'Briens are one of the oldest and noblest families in the ancient Kingdom of Thomond, now Clare, Limerick and part of Tipperary. This family history sests the O'Briens in context with the role that they have played throughout Irish history over the last 1,000 years. John O'Donoghue's Historical Memoir of the O'Briens was the first extensive contemporary history of this Sept, though it is now nearly nearly 150 years since it was published. It is significant therefore that Martin Breen is re-publishing this history as part of the Martin Boru Millennium celebrations to commemorate  the 1000th Anniversary of the accession of the O'Brien's illustrious ancestor, Brian Boru, to the throne of Ireland in 1002. It will be of significant interest to O'Briens the world over, who are clamouring for more readily available information on the history of their clan.