Sir Humphrey Edmund de Trafford, 4th Baronet, MC, DL (30 November 1891 – 6 October 1971) was a prominent English racehorse owner, and the grandfather of Brigadier Andrew Henry Parker Bowles. He was the son of Sir Humphrey de Trafford, 3rd Baronet, and Violet Alice Maud Franklin.
Trafford was educated at The Oratory School and the Royal Military College, Sandhurst. After training he was commissioned into the Coldstream Guards as an officer. He fought with distinction in the First World War and was awarded the Military Cross in 1917.
He married the Hon. Cynthia Hilda Evelyn Cadogan, daughter of Henry Arthur Cadogan, Viscount Chelsea and the Hon. Mildred Cecilia Harriet Sturt, on 2 October 1917. They had four daughters:
Trafford was an amateur rider and racehorse owner and a member of the Jockey Club and its National Hunt Committee.
In 1926, he purchased the Newsells Park Estate, Barkway near Royston, Hertfordshire as a home for his family and established a stud farm there, from which he bred most of his famous racehorses including Alcide who won the 1958 St. Leger Stakes and the 1959 King George VI and Queen Elizabeth Stakes and Parthia, who won the 1959 Epsom Derby. Other notable horses included Papillio who won the 1953 Goodwood Stakes and Approval who won the Observer Gold Cup at Doncaster in 1969 and the Dante Stakes at York in 1970. Trafford also served as Steward of The Jockey Club from 1934–37 and then again in 1944 and 1951.