Gavin Campbell, 1st Marquess of Breadalbane KG (9 April 1851 – 19 October 1922), styled Lord Glenorchy between 1862 and 1871 and known as The Earl of Breadalbane and Holland between 1871 and 1885, was a Scottish nobleman and Liberal politician.
Breadalbane served as a lieutenant in the 4th Battalion, Argyll and Sutherland Highlanders from 1873 to 1874. He was later in the Shropshire Yeomanry, from entering as Sub-Lieutenant in 1877, being promoted lieutenant in 1882, retiring as captain in 1887. From 1897 to 1910 he was Lieutenant-Colonel commanding the Highland Cyclist Battalion, of which he became Honorary Colonel in 1913, and was an Aide-de-Camp to King Edward VII in 1903.
As his earldom was a Scottish peerage it did not entitle him to an automatic seat in the House of Lords. However, in 1873 he was created Baron Breadalbane, of Kenmure in the County of Perth, in the Peerage of the United Kingdom, which gave him a seat in the House of Lords. That same year he was appointed a Lord-in-waiting in the Liberal administration of William Ewart Gladstone. The Liberals fell from power in 1874 but returned to office in 1880, when Breadalbane was sworn of the Privy Council and appointed Treasurer of the Household by Gladstone, a post he held until 1885. The latter year he was created Earl of Ormelie, in the County of Caithness, and Marquess of Breadalbane, in the Peerage of the United Kingdom.
Lord Breadalbane did not serve in Gladstone's brief 1886 administration, but once again held office as Lord Steward of the Household from 1892 to 1895, firstly under Gladstone and from 1894 under the premiership of Lord Rosebery. In 1894 he was appointed a Knight of the Garter. He also served as Lord High Commissioner to the General Assembly of the Church of Scotland in 1893, 1894 and 1895 and as Lord Lieutenant of Argyllshire from 1914 until 1922 and was the last holder of the office of Keeper of the Privy Seal of Scotland, which he held from 1907 until his death in 1922 in Glasgow.
He was a Knight of the Order of the Seraphim of Sweden and a Knight of Justice of the Order of St John of Jerusalem (KStJ), in which capacity he represented King Edward VII during the dedication in June 1902 of the restored chapel at Marienburg Castle, originally the seat of the Teutonic Order. He was awarded the silver medal of the Royal Humane Society, and was also a Brigadier-General of the Royal Company of Archers.