Mary, Countess Cowper (née Mary Clavering) (1685 – February 5, 1724) was an English courtier and diarist, and the wife of William Cowper, 1st Earl Cowper.
In 1706, September, William Cowper secretly married the beautiful 20 year old Mary, daughter of John Clevage, of Chopwell, Durham after his first wife died in 1705. In November of the same year he succeeded to his father's baronetcy and in December he was raised to the peerage as Baron Cowper of Wingham, Kent.
In May 1707 Queen Anne in Council named William Cowper the first Lord High Chancellor of Great Britain and he was later appointed one of the Lords Justices responsible for governing the country until George I arrived in England after Queen Anne's death.
As Lady of the Bedchamber to Caroline, Princess of Wales, Mary immediately put her new-found access to court and her fluent French to use in acting as a go-between for her husband. The first day she attended the Princess she gave her Bernstorff’s 'A Treatise on the State of Parties' which she 'had transcribed and translated for my Lord, in French and English, to give the King'
In April 1718 Earl Cowper resigned office and retired to Colne Green, his home in the country, but Mary remained at Court as Lady of the Bedchamber to Caroline, Princess of Wales and in her diaries wrote an account of events at Court. Some of the diaries were destroyed by Mary but the diaries covering October 1714 to October 1716 and April and May 1720 were later published by Charles Spencer Cowper in 1864.
Lord Cowper died after a short illness on the 10th of October 1723 at his residence, Colne Green, in Hertford, built by himself in 1704 (demolished by the 5th Earl in 1801 on advice from the landscape designer Repton) nearby to which the later mansion of Panshanger was built in 1840 (and also sadly demolished in 1954). Mary died grief stricken several months later. The 1st Earl and Mary left two sons and two daughters. Mary was the great aunt (by marriage) of William Cowper, the poet.