Mervyn Tuchet, 4th Earl of Castlehaven (died 2 November 1686) was the third son of Mervyn Tuchet, 2nd Earl of Castlehaven, and his first wife, Elizabeth Barnham (1592 - ). He succeeded his brother James Tuchet as Earl of Castlehaven on 11 October 1684. He also held the subsidiary titles 14th Baron Audley and 2nd Baron Audley of Hely.
Marriage and issue
He married Mary Talbot (buried 15 March 1710/1 in Clewer, Berkshire), 3rd daughter of John Talbot, 10th Earl of Shrewsbury (ante 1601–1654) and his wife, Mary, daughter of Sir Francis Fortescue.
thumb|Ledger stone of Mary Tuchet, wife of Sir Henry Wingfield, 4th Baronet. All Saints Church, Easton, Suffolk
They had the following children:
- James Tuchet, 5th Earl of Castlehaven (died 9 August 1700), He had at the age of 16 succeeded his elder brother Sir Robert Wingfield, 3rd Baronet (c. 1652–c. 1671). He left two sons:
- Henry Wingfield (died 1712) Married without issue male