The beginning of the Gospel of Mark from the Book of Durrow.

Insular script was a medieval script so called because it was used in Ireland, Britain, and Scotland. It later spread to Continental Europe in centres under the influence of Celtic Christianity.

The script developed in Ireland in the 7th century and was used as late as the 19th century. It was closely related to the uncial and half-uncial scripts, its immediate influences; Irish insular is sometimes called Irish half-uncial.

Works written in insular commonly use large initial letters surrounded by red ink dots (although this is also true of other scripts written in Ireland and England). Letters often gradually diminish in size as they are written across a line or a page, and letters with ascenders (b, d, h, l, etc.) are written with triangular or wedge-shaped tops. The bows of letters such as b, d, p, and q are very wide. The script uses many ligatures and has many unique abbreviations, along with many borrowings from Tironian notes.

Insular script was spread to England by Irish missionaries; previously, uncial script had been brought to England by Augustine of Canterbury. The influences of both scripts produced a separate English insular form, which existed in both a majuscule and a minuscule form. The majuscule was used mostly in the 7th and 8th centuries, while the minuscule form was used until the 12th century, when it had become heavier and more angular than its Irish counterpart. Irish missionaries also brought the script to Europe, where they founded monasteries such as Bobbio and Fulda.

The script was used not only for Latin religious books, but also for every other kind of book, including vernacular works. Examples include the Book of Kells, the Cathach of St. Columba, the Ambrosiana Orosius, the Durham Cathedral Library A. II. 10. Gospel Book Fragment, the Book of Durrow the Durham Gospels, the Echternach Gospels, the Lindisfarne Gospels, the Lichfield Gospels, the St. Gall Gospel Book, and the Book of Armagh.

Insular script was influential in the development of Carolingian minuscule in the scriptoria of the Carolingian empire.

See also: List of Hiberno-Saxon illustrated manuscripts