Comhairle nan Eilean Siar is the only local council in Scotland to have a Gaelic-only name. The original name, Western Isles Council, was retracted in 1997 under the Local Government (Gaelic Names) (Scotland) Act 1997, and the former "Western Isles" council area is now officially named "Na h-Eileanan Siar", even in English language contexts.
In 1975, the council was created as Western Isles Council, 57 years after the creation of Na h-Eileanan an Iar for elections to the House of Commons of the Parliament of the United Kingdom (the constituency being named, when created, Western Isles). Since 1999, there has been also the Na h-Eileanan an Iar constituency of the Scottish Parliament, with the same boundaries.
When the Bank of Credit and Commerce International collapsed in 1991, the then Western Isles Council lost £35m invested there, compelling a large increase in its council tax rate.
In 1997, the Western Isles Council was renamed as Comhairle nan Eilean Siar.
General elections to the council are held on a five-year cycle. The next is due in 2022.
From 1975 until 2007, council elections used the first past the post system of election; the last elections of this type elected 31 councillors, elected by 31 single-member wards.
In 2007, under the Local Governance (Scotland) Act 2004, the single transferable vote system, together with multi-member wards, was used for the first time, each ward electing three or four councillors. This system is designed to produce a form of proportional representation.
Following the 2017 election, resulted in the following composition: