Title Date of creation Surname Current status Notes O'Brien of Ardtona [1] 1916 O'Brien extinct 1916 first Baronet created Baron Shandon in 1918 O'Brien of Kilfenora [2] 1891 O'Brien extinct 1914 first Baronet created Baron O'Brien in 1900 O'Brien of Merrion Square and Borris-in-Ossory [3] 1849 O'Brien dormant Lord Mayor of Dublin ; sixth Baronet died 1982 O'Loghlen of Drumcanora [4] 1838 O'Loghlen extant O'Malley of Rosehill [5] 1804 O'Malley extinct 1892 O'Connell of Lakeview [6] 1869 O'Connell extant O'Neill of Cleggan [7] 1929 O'Neill extant first Baronet created Baron Rathcavan in 1953 Oakes of Hereford [ citation needed ] 1815 Oakes extinct 1927 first Baronet had already been created a Baronet in 1813, which creation became extinct in 1822 Oakes of Nassau [8] 1939 Oakes extant Oakes of the Army [ citation needed ] 1813 Oakes extinct 1822 first Baronet obtained a new patent in 1815, which creation became extinct in 1927 Oakshott [9] 1959 Oakshott extant first Baronet created a life peer as Baron Oakshott in 1964, which title became extinct in 1975 Ochterlony of Ochterlony [ citation needed ] 1823 Ochterlony extinct 1964 had already been created Baronet of Pitforthy in 1816, which title became extinct in 1825 Ochterlony of Pitforthy [10] 1816 Ochterlony extinct 1825 also created Baronet of Ochterlony in 1823, which title became extinct in 1964 Ogle of Worthy [11] 1816 Ogle extinct 1940 Ohlson of Scarborough [12] 1920 Ohlson extant Oppenheimer of Stoke Poges [13] 1921 Oppenheimer extinct 2020 Ormsby of Cloghans [14] 1812 Ormsby extinct 1833 Orr-Ewing of Ballikinran [15] 1886 Orr-Ewing extant Orr-Ewing of Hendon [16] 1963 Orr-Ewing extant first Baronet created a life peer as Baron Orr-Ewing in 1971, which title became extinct in 1999 Orr-Lewis of Whitewebbs Park [12] 1920 Orr-Lewis extinct 1980 Osler of Norham Gardens [17] 1911 Osler extinct 1919 Otway of Brighthelmstone [18] 1831 Otway extinct 1912 Ouseley of Claremont [19] 1808 Ouseley extinct 1889 Outram of The Bengal [20] 1858 Outram extant Owen of Orielton [14] 1813 Owen extinct 2002