Kavanagh was born at Borris House in County Carlow, the son of Thomas Kavanagh Member of Parliament and Lady Harriet Margaret Le Poer Trench, daughter of the second Earl of Clancarty. His father traced his lineage to the ancient Kings of Leinster through Art MacMurrough-Kavanagh.
Arthur MacMorrough Kavanagh travelled extensively in Egypt, Anatolia, Persia, and India between 1846 and 1853. In India, his letter of cr from his mother was cancelled when she discovered that he had spent two weeks in a harem, so he persuaded the East India Company to hire him as a despatch rider. Together, they had seven children: Eva (died 1896), May (died 1949), Agnes (died 1932), Walter (died 1922), Arthur (died 1882), Charles (died 1950), and Osborne (died 1897). Kavanagh served as High Sheriff of County Kilkenny for 1856 and High Sheriff of Carlow for 1857. On being elected, he had to be placed on the Tory benches by his manservant.
The Speaker, Evelyn Denison, gave a special dispensation to allow the manservant to stay in the chamber during sittings. Kavanagh was opposed to the disestablishment of the Irish Church, but supported the Land Acting of 1870.
On losing his seat in 1880, William Ewart Gladstone appointed him to the Bessborough Commission, but he disagreed with its conclusions and published his own dissenting report.
Arthur MacMorrough Kavanagh was a most philanthropic landlord, and was an active county magistrate and chairman of the board of guardians.
daughter of the second Earl of Clancarty
served as MP for County Carlow from 1908 to 1910.
