Scottish Gaelic (Scottish Gaelic: Gàidhlig [ˈkaːlɪkʲ] (listen)), also known as Scots Gaelic and Gaelic, is a Goidelic language (in the Celtic branch of the Indo-European language family) native to the Gaels of Scotland. As a Goidelic language, Scottish Gaelic, as well as both Irish and Manx, developed out of Old Irish. It became a distinct spoken language sometime in the 13th century in the Middle Irish period, although a common literary language was shared by the Gaels of both Ireland and Scotland until well into the 17th century. Most of modern Scotland was once Gaelic-speaking, as evidenced especially by Gaelic-language place names.

In the 2011 census of Scotland, 57,375 people (1.1% of the Scottish population aged over 3 years old) reported being able to speak Gaelic, 1,275 fewer than in 2001. The highest percentages of Gaelic speakers were in the Outer Hebrides. Nevertheless, there is a language revival, and the number of speakers of the language under age 20 did not decrease between the 2001 and 2011 censuses. Outside Scotland, a dialect known as Canadian Gaelic has been spoken in eastern Canada and Glengarry County, Ontario since the 18th century. In the 2016 national census, nearly 4,000 Canadian residents claimed knowledge of Scottish Gaelic, with a particular concentration in Nova Scotia.

Scottish Gaelic is not an official language of the United Kingdom. However, it is classed as an indigenous language under the European Charter for Regional or Minority Languages, which the UK Government has ratified, and the Gaelic Language (Scotland) Act 2005 established a language-development body, Bòrd na Gàidhlig.