| Honorific-Prefix: | Sir |
| Timothy O'Brien | |
| Office: | Member of Parliament for Cashel |
| Term Start: | 5 February 1846 |
| Term End: | 6 May 1859 |
| Predecessor: | Joseph Stock |
| Successor: | John Lanigan |
| Office1: | Lord Mayor of Dublin |
| Term Start1: | 1849 |
| Term End1: | 1850 |
| Predecessor1: | Jeremiah Dunne |
| Successor1: | John Reynolds |
| Term Start2: | 1844 |
| Term End2: | 1845 |
| Predecessor2: | George Roe |
| Successor2: | John L. Arabin |
| Birth Date: | 1787 |
| Nationality: | Irish |
| Party: | Whig |
| Children: | Sir Patrick O'Brien, 2nd Baronet (son) |
Sir Timothy O'Brien, 1st Baronet (1787 – 3 December 1862)[1] was an Irish Whig, Independent Irish Party and Repeal Association politician, and merchant.[2] [3]
He was the son of Timothy O'Brien and his wife (née Madden). In 1821, he married Catherine Murphy, daughter of Edward Murphy, and they had at least five children: Timothy (died 1869); John (died 1869); Kate (died 1894); Ellen (died 1899); and Patrick (1823–1895).
In 1844, O'Brien was made Lord Mayor of Dublin, a position he again held in 1849.[4] Simultaneously, he was a Member of Parliament (MP), first elected as a Repeal Association member for Cashel at a by-election in 1846—caused by the resignation of Joseph Stock. Becoming an Independent Irish MP in 1852[2] and a Whig in 1857,[3] he held the seat until the 1859 general election, when he did not seek re-election.[5]
In 1849, during Queen Victoria's first visit to Ireland, O'Brien was made a baronet, becoming 1st baronet of Merrion Square and Boris-in-Ossory. Upon his own death in 1862, the baronetcy was inherited by his son, Patrick O'Brien.[6]
Outside of his political career, O'Brien was also a Justice of the Peace and a Deputy Lieutenant.