Captain Hugh de Grey Seymour, 6th Marquess of Hertford CB PC TD JP (22 October 1843 – 23 March 1912), styled Earl of Yarmouth from 1870 to 1884, was a British soldier, courtier and Conservative politician.

He became known by the courtesy title Earl of Yarmouth when his father succeeded to the marquessate of Hertford in 1870.

He was appointed an aide-de-camp to King Edward VII in the 1902 Coronation Honours list on 26 June 1902,[2] with the regular rank of colonel.

[1][6] In 1879 he was sworn of the Privy Council[7] and appointed Comptroller of the Household under Lord Beaconsfield,[8] a post he retained until the government fell the following year.

They had eight children: The Marchioness of Hertford died in April 1909, aged 62, while on a voyage to Palestine.