Horatio Walpole, 1st Baron Walpole of Wolterton (8 December 1678 - 1757), English diplomatist, was a son of Robert Walpole of Houghton , Norfolk, and a younger brother of the great Sir Robert Walpole.

The Walpoles owned land in Norfolk in the 12th century and took their name from Walpole, a village in the county. An early member of the family was Ralph de Walpole , bishop of Norwich from 1288 to 1299, and bishop of Ely from 1299 until his death on the 20th of March 1302. Among its later members were three brothers, Edward (1560-1637), Richard (1564-1607) and Michael (1570-1624), all members of the Society of Jesus. Another Jesuit in the family was Henry Walpole (1558-1595), who wrote An Epitaph of the life and death of the most famous clerk and virtuous priest Edmund Campion. After an adventurous and courageous career in the service of the order, he was arrested on landing in England, was tortured and then put to death on the 17th of April 1595

Born at Houghton and educated at Eton and King's College, Cambridge, Horatio Walpole became a fellow of King's and entered parliament in 1702, remaining a member for fifty-four years. In 1715, when his brother, Sir Robert, became first lord of the treasury, he was made secretary to the treasury, and in 1716, having already had some experience of the kind, he went on a diplomatic mission to The Hague. He left office with his brother in 1717, but he was soon in harness again, becoming secretary to the lord-lieutenant of Ireland in 1720 and secretary to the treasury a second time in 1721.

In 1722 he was again at The Hague, and in 1723 he went to Paris, where in the following year he was appointed envoy extraordinary and minister plenipotentiary . He got on intimate terms with Fleury and seconded his brother in his efforts to maintain friendly relations with France; he represented Great Britain at the congress of Soissons and helped to conclude the treaty of Seville (November 1729). He left Paris in 1730 and in 1734 went to represent his country at The Hague, where he remained until 1740, using all his influence in the cause of European peace.

After the fall of Sir Robert Walpole in 1742 Horatio defended his conduct in the House of Commons and also in a pamphlet, "The Interest of Great Britain steadily pursued". Later he wrote an "Apology", dealing with his own conduct from 1715 to 1739, and an "Answer" to the latter part of Lord Bolingbroke's letters on the study of history (printed 1763).

In 1756 he was created Baron Walpole of Wolterton, this being his Norfolk seat, and he died on the sth of February 1757.

His eldest son, Horatio, the 2nd baron (1723-1809), was created earl of Orford in 1806, and one of his sons was Major-General George Walpole (1758-1835), under-secretary for foreign affairs in 1806.

See W. Coxe , Memoirs of Horatio, Lord Walpole (2nd ed., 1808); the same writer, Memoirs of Sir Robert Walpole (1816); and Charles, comte de Baillon , Lord Walpole d, la cour de France (1867).