Uncial is a majuscule script written entirely in capital letters and commonly used from the 4th to 8th centuries AD by Latin and Greek scribes.

Early uncial script likely developed from late Old Roman cursive. Early forms are characterized by broad single stroke letters using simple round forms taking advantage of the new parchment and vellum surfaces, as opposed to the angular, multiple stroke letters, which are more suited for rougher surfaces, such as papyrus. In the oldest examples of uncial, such as the fragment of De bellis macedonicis in the British Library, of the late 1st-early 2nd century, all of the letters are disconnected from one another, and word separation is typically not used. Word separation, however, is characteristic of later uncial usage.

As the script evolved over the centuries, the characters became more complex. Specifically flourishes and exaggerations of the basic strokes began to appear in more manuscripts. Ascenders and descenders were the first major alterations, followed by twists of the tool in the basic stroke and overlapping. By the time the more compact minuscule scripts arose circa AD 800, some of the evolved uncial styles formed the basis for these simplified, smaller scripts. Uncial was still used, particularly for copies of the Bible, tapering off until around the 10th century. There are over 500 surviving copies of uncial script, by far the largest number prior to the Carolingian Renaissance.

There is some doubt about the original meaning of the word. Uncial itself probably comes from St. Jerome's preface to the Book of Job, where it is found in the form uncialibus, but it is possible that this is a misreading of inicialibus, and Jerome may have been referring to the larger initial letters found at the beginning of paragraphs.