Sir William Trumbull, PC (8 September 1639 – 14 December 1716) was an English diplomat and politician who was a member of the First Whig Junto.

After completing his degree, he visited France and Italy, where he met several distinguished persons, such as Lords Sunderland and Godolphin, Algernon Sidney and Henry Compton.

[2] He was admitted an advocate in Doctors' Commons in London on 28 April 1668 and began practising in the ecclesiastical and admiralty courts.

Through the offices of his father-in-law, Sir Charles Cotterell, he was appointed chancellor of the diocese of Rochester in 1671 by its bishop, John Dolben, the future archbishop of York, and benefited much from 'the friendship and patronage of that great and good man'.

[3] In 1683 he was appointed Judge Advocate of the Fleet by Lord Dartmouth, George Legge, in an expedition to evacuate the British colony at Tangier, where he was to act as commissioner for settling the leases of the houses between the King and the inhabitants.

Samuel Pepys, who was also on the expedition, was unimpressed – "Strange to see how surprised and troubled Dr. Trumbull shows himself at this new work put on him of a judge-advocate; how he cons over the law-martial and what weak questions he asks me about it."

With King James a declared papist and French King Louis XIV persecuting his Protestant subjects, Trumbull, a devout Anglican, was an odd choice for the post, being a zealous opponent of Roman Catholicism, and did much to benefit the condition of the English Protestants in France after Edict of Fontainebleau.

[4] Dryden records, in the postscript to his translation of Virgil, that "if the last Aeneid shine amongst its fellows, it is owing to the commands of Sir William Trumbull, who recommended it as his favourite to my care."

In 1670, Trumbull married Elizabeth,[5] daughter of Sir Charles Cotterell,[6] Master of the Ceremonies; she died in 1704, they having had no children.

In Scotland in October 1706, he married Judith (died 1724), daughter of Henry Alexander, the 4th Earl of Stirling.