Robert King, 6th Earl of Kingston (17 July 1804 – 16 October 1869), styled The Honourable until 1854, was an Anglo-Irish politician and peer.
He was the son of Robert King, 1st Viscount Lorton and Lady Frances Parsons, daughter of Laurence Parsons, 1st Earl of Rosse. He was educated at Trinity College, Dublin, matriculating in 1823.
He represented Roscommon in the House of Commons of the United Kingdom between 1826 and 1830, and served as High Sheriff of Roscommon in 1836. On 20 November 1854 he succeeded to his father's titles as Viscount Lorton. On 8 September 1869 he succeeded his cousin, James King, 5th Earl of Kingston, as Earl of Kingston, but died the following month.
He married Anne Gore-Booth, daughter of Sir Robert Newcomen Gore-Booth, 3rd Baronet and Hannah Irwin, on 7 December 1829. A son, Robert Edward, was born 18 October 1831, and they had a daughter, Frances Isabella Anna, who died 8 October 1890.
By the mid-1830s, King had suffered a stroke and the effects of his heavy drinking, and was "almost entirely under the influence of his wife", whose "high-living" was disliked by his father, Viscount Lorton. In 1846, she had formed a relationship with "dubious and insolvent French nobleman" Vicomte Ernest Valentin de Satgé St. Jean; when her son, Henry, was born 31 July 1848, King disowned the child, but he continued to live with his wife and her lover despite his father's protests. King's attempt to sue for divorce in 1850 failed due to his own extramarital affair, with his nursemaid and travelling companion Julie Imhoff, being established.
The King family "were driven to extraordinary lengths" in attempting to stop King's estranged wife and her French lover from gaining control of their property, and so, when on the death of the 7th Earl of Kingston on 21 June 1871, Henry (31 July 1848 – 13 January 1896) succeeded as 8th Earl- his "legitimacy... confirmed (as it could not be disproved) at the probate court in Dublin in 1870"- the "disastrously dispersed hereditary lands" did not come to him with the title.