Thomas West, 9th Baron De La Warr and 6th Baron West (c. 1475 – 25 September 1554) was the eldest son of Thomas West, 8th Baron De La Warr, by his second wife, Elizabeth Mortimer, daughter of Sir Hugh Mortimer of Martley and Kyre Wyard, Worcestershire, by Eleanor Cornwall, daughter of Sir Edmund Cornwall.

He was disinherited by an act of parliament in 1550, although he had been reinstated as heir by the time of his uncle's death.Despite the fact that he had been reinstated as heir by his uncle, when the latter died in 1554 William West was unable to inherit the barony of de la Warr as a result of the Act of Parliament of 1550 which had deprived him of all honours.

Two years later he was involved in the Dudley conspiracy, and on 30 June 1556 was arraigned at the Guildhall on charges of treason, to which he responded as "William, Lord de la Warr", forcing the heralds to prove during the trial that he was not entitled to the barony and therefore not entitled to a trial by his peers in the House of Lords.

He fought at the siege of St. Quentin in that year, and in 1563, early in the reign of Queen Elizabeth, was restored in blood.

On 5 February 1570 he was knighted, and on the same day created Baron De La Warr, which was regarded as a new creation of the title.