Rich, Mary (1624/5–1678), countess of Warwick , noblewoman, was the seventh daughter and thirteenth child of Richard Boyle (qv), 1st earl of Cork, and his second wife, Catherine (d. 1630), daughter of Sir Geoffrey Fenton (qv), secretary of state for Ireland. She was the sister of Roger Boyle (qv), 1st earl of Orrery, and Robert Boyle (qv), chemist and proponent of Boyle's law. After the death of her mother, she was raised and educated by Lady Clayton, wife of Sir Randall Clayton, at Mallow in Co. Cork. She returned to her father in 1638, going to the family house at Stalbridge in Dorset, where she was presented with the earl of Cork's arrangements for her marriage to James Hamilton, second son of the earl of Clandeboye. Cork was furious when his ‘unruly daughter’ refused to marry Hamilton and stopped, for a time, her annual allowance of £100 while family members tried unsuccessfully to persuade her to reconsider the proposed match.
Through her sister-in-law Katherine Boyle (née Kilgrew), Mary met Charles Rich (1616–73), second son of the earl of Warwick, while he was a courtier in London, and a secret romance developed between the couple. The earl of Cork became aware of the relationship when Rich displayed concern for Mary during a bout of measles. On her recovery, she was banished to Hampton Court, the earl's country residence, where Rich continued to visit her. Mary stubbornly informed her family that, although she would not marry Rich without consent, she would not marry anyone else. Her father finally relented and, on 21 July 1641, the couple were privately married at Shepperton, near Hampton Court. Cork was persuaded to part with her dowry of £7,000, though it was not fully paid at the time of his death in 1643.
After her marriage, Mary Rich went to live at Leighs in Essex, the principal residence of the earls of Warwick, where she had a good relationship with her husband's family. In 1642 she gave birth to a daughter, Elizabeth, who died just over a year later and, on 28 September 1643, she had a second child, Charles, who died of smallpox in May 1664. Mary had no further children, despite her desire to, but she did become heavily involved in the raising of various nieces at Leighs. During the civil war her husband fought on the parliamentary side and, in 1646, the royalists raided her house in search of arms. Charles Rich succeeded as fourth earl of Warwick in 1659, after the recent deaths of both his father and his elder brother. Already suffering from gout, Rich gradually became more disabled and, in the years preceding his death in 1673, he was increasingly abusive towards his wife. With no surviving children, the title passed to his cousin Robert, second earl of Holland, while Mary was left with the responsibility of disposing of his considerable estate.
In July 1666 Mary Rich began to keep a diary, which she continued to write until November 1677. She developed a strong religious temperament, going to her ‘wilderness’ garden several times a day to pray and meditate. Her house became a centre for puritan ministers and Rich, renowned as a pious lady, was also well known for her many charitable works. Although she occasionally attended the court and maintained contact with her sister Lady Ranelagh (qv) and others during the 1660s, she preferred the peace and beauty of Leighs. Her diary and meditations provide a valuable insight into the life of a seventeenth-century lady. She died 12 April 1678 at Leighs and was buried at Felsted church. In 1686 her chaplain, Anthony Walker, published her funeral sermon, entitle The virtuous woman found. There are portraits of Mary Rich, countess of Warwick, in the Mansell collection and in the British Museum, which also holds most of her remaining diaries and meditations.