The County of Bute (Scottish Gaelic: Siorrachd Bhòid), also known as Buteshire, is a historic county and registration county of Scotland. It comprised a number of islands in the Firth of Clyde, between the counties of Argyll and Ayr, the principal islands being Bute, Arran, Great Cumbrae and Little Cumbrae. The county town was Rothesay, located on the island of Bute. The County of Bute had its own elected county council from 1890 to 1975.

The historic County of Bute was divided between new council areas with implementation of the Local Government etc. (Scotland) Act 1994, on the 1 April 1996. The new Argyll and Bute Council area was given responsibility for island of Bute itself, while the island of Arran and The Cumbraes were added to the new North Ayrshire Council area.

Buteshire was created as a shire (the area administered by a sheriff) by Robert II around 1385. Prior to that the islands in the Firth of Clyde had not formed part of any shire. The position of Sheriff of Bute was initially given to Robert's illegitimate son, John Stewart, and subsequently passed to John's descendants, who became the Earls of Bute in 1703.

Inherited sheriffdoms were abolished by the Heritable Jurisdictions (Scotland) Act 1746, after which sheriffs were appointed by the crown. The Sheriffs (Scotland) Act 1747 then placed Buteshire under a joint sheriff with neighbouring Argyll.

Meanwhile, in 1667 Commissioners of Supply were established for each shire, which would serve as the main administrative body for the area until the creation of county councils in 1890. Elected county councils were created in 1890 under the Local Government (Scotland) Act 1889, taking most of the functions of the Commissioners of Supply. The County of Bute Council was based at the Rothesay Town Hall and County Buildings at 31 High Street in Rothesay, which had been built in 1835 and served as the meeting place for Rothesay Town Council and the Commissioners of Supply, as well as being the courthouse for Buteshire.

The County of Bute was abolished for local government purposes in 1975 under the Local Government (Scotland) Act 1973, which replaced Scotland's counties, burghs and landward districts, with upper-tier regions and lower-tier districts. The County of Bute was included in the Strathclyde region, with the Isle of Bute being placed in the Argyll district, and the Isle of Arran and the Cumbraes being placed in Cunninghame district. Strathclyde region was abolished in 1996 when the regions and districts were replaced by unitary council areas, with Argyll and Bute becoming a council area, and Cunninghame being renamed to become the North Ayrshire council area.

The County of Bute historic boundaries are still used for some limited official purposes connected with land registration, being a registration county.

The County of Bute consisted of two main islands in the Firth of Clyde separated by the Sound of Bute: Arran (also including the much smaller Holy Island, Hamilton Isle and Pladda off the south-east coast); and Bute (including the small isle of Inchmarnock off its west coast); and also the Cumbraes between Bute and Ayrshire on the mainland, comprising Great Cumbrae, Little Cumbrae and the islets of The Eileans, Broad Islands, Castle Island and Trail Island.