Bute, the most important, though not the largest, of the islands constituting the county of the same name, in the Firth of Clyde, Scotland, about 18 m. S.W. of Greenock and 40 m., by water, from Glasgow. It is bounded on the N. and W. by the lovely Kyles of Bute, the narrow winding strait which separates it from Argyllshire, on the E. by the Firth of Clyde, and on the S. and S.W. by the Sound of Bute, about 6 m. wide, which divides it from Arran. Its area is about 49 sq. m., or 31,161 acres. It lies in a N.W. to S.E. direction, and its greatest length from Buttock Point on the Kyles to Garroch Head on the Firth of Clyde is 15½ m. Owing to indentations its width varies from 1⅓ m. to 4½ m. There are piers at Kilchattan, Craigmore, Port Bannatyne and Rothesay, but Rothesay is practically the harbour for the whole island. Here there is regular communication by railway steamers from Craigendoran, Prince's Pier (Greenock), Gourock and Wemyss Bay, and by frequent vessels from the Broomielaw Bridge in Glasgow and other points on the Clyde. Pop. (1891) 11,735; (1901) 12,162.

The principal hills are in the north, where the chief are Kames Hill (911 ft.) and Kilbride Hill (836 ft.). The streams are mostly burns, and there are six lochs. Loch Fad, about 1 m. S. of Rothesay, 2½ m. long by ⅓ m. wide, was the source of the power used in the Rothesay cotton-spinning mill, which was the first establishment of the kind erected in Scotland. In 1827 on its western shore Edmund Kean built a cottage afterwards occupied by Sheridan Knowles. It now belongs to the marquess of Bute. From Loch Ascog, fully 1 m. long, Rothesay derives its water supply. The other lakes are Loch Quien, Loch Greenan, Dhu Loch and Loch Bull. Glen More in the north and Glen Callum in the south are the only glens of any size. The climate is mild and healthful, fuchsias and other plants flowering even in winter, and neither snow nor frost being of long continuance, and less rain falling than in many parts of the western coast. Some two-thirds of the area, mostly in the centre and south, are arable, yielding excellent crops of potatoes for the Glasgow market, oats and turnips; the rest consists of hill pastures and plantations. The fisheries are of considerable value. There is no lack of sandstone, slate and whinstone.

Some coal exists, but it is of inferior quality and doubtful quantity. At Kilchattan a superior clay for bricks and tiles is found, and grey granite susceptible of high polish.

The island is divided geologically into two areas by a fault running from Rothesay Bay in a south-south-west direction by Loch Fad to Scalpsie Bay, which, throughout its course, coincides with a well-marked depression. The tract lying to the north-west of this dislocation is composed of the metamorphic rocks of the Eastern Highlands. The Dunoon phyllites form a narrow belt about a mile and a half broad crossing the island between Kames Bay and Etterick Bay, while the area to the north is occupied by grits and schists which may be the western prolongations of the Beinn Bheula group. Near Rothesay and along the hill slopes west of Loch Fad there are parallel strips of grits and phyllites. That part of the island lying to the east of this dislocation consists chiefly of Upper Old Red Sandstone strata, dipping generally in a westerly or south-westerly direction. At the extreme south end, between Kilchattan and Garroch Head, these conglomerates and sandstones are overlaid by a thick cornstone or dolomitic limestone marking the upper limit of the formation, which is surmounted by the cement-stones and contemporaneous lavas of Lower Carboniferous age.

The bedded volcanic rocks which form a series of ridges trending north-west comprise porphyritic basalts, andesite, and, near Port Luchdach, brownish trachyte. Near the base of the volcanic series intrusive igneous rocks of Carboniferous age appear in the form of sills and bosses, as, for instance, the oval mass of olivine-basalt on Suidhe Hill. Remnants of raised beaches are conspicuous in Bute. One of the well-known localities for arctic shelly clays occurs at Kilchattan brick-works, where the dark red clay rests on tough boulder-clay and may be regarded as of late glacial age.

As to the origin of the name of Bute, there is some doubt. It has been held to come from both (Irish for "a cell"), in allusion to the cell which St Brendan erected in the island in the 6th century; others contend that it is derived from the British words ey budh (Gaelic, ey bhiod), "the island of corn" (i.e. food), in reference to its fertility, notable in contrast with the barrenness of the Western Isles and Highlands. Bute was probably first colonized by the vanguard of Scots who came over from Ireland, and at intervals the Norsemen also secured a footing for longer or shorter periods. In those days the Butemen were also called Brandanes, after the Saint. Attesting the antiquity of the island, "Druidical" monuments, barrows, cairns and cists are numerous, as well as the remains of ancient chapels. In virtue of a charter granted by James IV. in 1506, the numerous small proprietors took the title of "baron," which became hereditary in their families. Now the title is practically extinct, the lands conferring it having with very few exceptions passed by purchase into the possession of the marquess of Bute, the proprietor of nearly the whole island. His seat, Mount Stuart, about 4½ m. from Rothesay by the shore road, is finely situated on the eastern coast.

Port Bannatyne (pop. 1165), 2 m. north by west of Rothesay, is a flourishing watering-place, named after Lord Bannatyne (1743-1833), a judge of the court of session, one of the founders of the Highland and Agricultural Society in 1784. Near to it is Kames Castle, where John Sterling, famous for Carlyle's biography, was born in 1806. Kilchattan, in the south-east of the island, is a favourite summer resort. Another object of interest is St Blane's Chapel, picturesquely situated about ½ m. from Dunagoil Bay. Off the western shore of Bute, ¾ m. from St Ninian's Point, lies the island of Inchmarnock, 2 m. in length and about ¾ m. in width.

See J. Wilson, Account of Rothesay and Bute (Rothesay, 1848); and J.K. Hewison, History of Bute (1894-1895).