William Dalrymple was a British Army officer and politician who sat in the Parliament of Great Britain and the Parliament of Ireland. In 1768, he was placed in command of a detachment of two regiments sent to Boston, Massachusetts, to support embattled royal officials who were having trouble enforcing the unpopular Townshend Acts. Troops in his command were involved in the Boston Massacre, in which five Bostonians were killed during a confrontation with a group of soldiers. In 1772-1773 Dalrymple received a local promotion to major general and commanded a force which captured the West Indian island of St Vincent. He returned to Britain in 1773. He continued to be in touch with his American Loyalist friends in Boston. He was saddened but not surprised by the Boston Tea Party.

After the American War of Independence broke out in 1775, Dalrymple returned to North America. He served as quartermaster general 1779-1783. He was promoted to brigadier general and then major general. After the end of the war Dalrymple was attacked for alleged corruption, but General William Howe stoutly defended his former subordinate and the allegations were dropped. Dalrymple then went into politics. He represented Wigtown Burghs in the British House of Commons from 1784 to 1790. Between 1796 and 1798 he sat for Duleek in the Irish House of Commons. Dalrymple was promoted to lieutenant general 1793 and general 1798. Lt. Governor of Royal Hospital Chelsea 22 Mar 1798 to 2 Apr 1804; and 19 Oct. 1804 to his death. He was Colonel of the 47th (Lancashire) Regiment of Foot from 1794 to his death.