British diplomat and statesman in the Walpole-Pelham era.

Educated at Eton College, Harrington was elected a member of Parliament for Derby in 1715, became envoy to Turin (1718–20), and was then ambassador to Spain (1720–27). As a reward for his successfully negotiating in 1729 the Treaty of Seville (Sevilla), which settled disputes between England and Spain, he was named secretary of state for the northern department by Sir Robert Walpole (Walpole, Robert, 1st earl of Orford) in May 1730. Although Harrington had the backing of George II, he was nonetheless unsuccessful in 1733 in persuading Walpole to support the Empire against France in the War of the Polish Succession. He again disagreed with Walpole in the early 1740s, favouring war with Spain and amity with France. In 1741 Harrington negotiated a treaty for the neutrality of Hanover without Walpole's knowledge.

When Walpole's government fell in 1742, Harrington lost his secretaryship, but in November 1744 he returned as secretary of state in the Pelham (Pelham, Henry) administration. When the king asked Harrington to desert the Pelhams' peace policy in February 1746, Harrington refused and joined Newcastle and the Pelhams in their joint resignation the same month. They formed a new ministry several days later, but Harrington had incurred the king's lasting hostility by being the first among them to resign. Harrington's eventual split with Newcastle over accepting French terms to end the war led to Harrington's resignation in October 1746. Through the agency of the Pelhams, to whom he had been intensely loyal, Harrington was appointed lord lieutenant of Ireland (serving until 1751).