Archibald Campbell, 3rd Duke of Argyll, 1st Earl of Ilay (June 1682 – 15 April 1761) was a Scottish nobleman, politician, lawyer, businessman and soldier. He was known as Lord Archibald Campbell from 1703 to 1706, and as the Earl of Ilay from 1706 until 1743, when he succeeded to the dukedom. He was the dominant political leader in Scotland in his day, and was involved in many civic projects.
Born at Ham House, Petersham, Surrey, he was the second son of Archibald Campbell, 10th Earl and 1st Duke of Argyll (1658–1703) and his wife Elizabeth, eldest daughter of Sir Lionel Talmash of Helmingham, Suffolk. He was the first cousin once removed of Lord William Campbell.
He was educated at Eton College and later at the University of Glasgow and then Utrecht University, where he studied civil law. He was appointed Lord High Treasurer of Scotland by Queen Anne in 1705.
He supported his brother, John Campbell, 2nd Duke of Argyll (on many topics, most notably the Act of Union), earning him the title of Earl of Ilay in 1706. Following the treaty of union he was elected as one of the sixteen Scottish peers to sit in the House of Lords.
His military career, which was less successful than his brother's, was somewhat distinguished. He obtained the Colonelcy of the newly formed 36th Regiment of Foot in 1701 and assisted his brother at the 1715 Battle of Sheriffmuir.
In 1711 he was appointed to the Privy Council. Many called him the "most powerful man in Scotland", at least until the era of Henry Dundas. Prime Minister Robert Walpole gave Campbell control over the royal patronage in Scotland. That became his base of power; he used it to control the votes of the other Scottish peers in the election of 16 representative peers to the British Parliament in London.
Lord Ilay played a critical role in establishing The Faculty of Medicine at the University of Edinburgh in 1726.
He was one of the founders of the Royal Bank of Scotland in 1727, and acted as the bank's first governor. His portrait has appeared on the front of all Royal Bank of Scotland banknotes, and as a watermark on the notes, since they were redesigned in 1987. The portrait is based on a painting by Allan Ramsay, in the Scottish National Portrait Gallery.
He succeeded his brother to the title of Duke of Argyll in October 1743. He worked on Inveraray Castle, his brother's estate, which was finished in the 1750s; however, he never lived in it, and he died in 1761. He is buried at Kilmun Parish Church.
He was married to Anne Whitfield about 1712, but had no legitimate male issue at his death. In his will, he left his English property to his mistress Ann (nee Shireburn) Williams. His titles passed to his cousin, the son of his father's brother John Campbell of Mamore.
The Duke established an estate at Whitton Park, Whitton in Middlesex in 1722 on land that had been enclosed some years earlier from Hounslow Heath. The Duke was an enthusiastic gardener and he imported large numbers of exotic species of plants and trees for his estate. He was nicknamed the 'Treemonger' by Horace Walpole. On his death, many of these, including mature trees, were moved by his nephew, the third Earl of Bute, to the Princess of Wales' new garden at Kew. This later became Kew Gardens and some of the Duke's trees are still to be seen there to this day. The Duke of Argyll's Tea Tree is an imported shrub named after him which has become established in hedgerows in some parts of England. One of his descendants, Jenny von Westphalen, was the wife of the famous German philosopher Karl Marx.