Roman square capitals, also called inscriptional capitals, elegant capitals and quadrata, are an ancient Roman form of writing, and the basis for modern capital letters.

Square capitals were used to write inscriptions, and less often to supplement everyday handwriting. For everyday writing the Romans used a current cursive hand known as Roman cursive. Notable examples of square capitals used for inscriptions are found on the Pantheon, Trajan's Column, and the Arch of Titus, all in Rome. Square capitals are characterized by sharp, straight lines, supple curves, thick and thin strokes, angled stressing and incised serifs. These Roman capitals are also called majuscules, as a counterpart to minuscule letters such as Merovingian and Carolingian.

In the early Middle Ages from the 4th century to the 6th century, square capitals were used to write de luxe copies of the works of pagan authors, especially Virgil, whose works make up the only three surviving manuscripts using this letter (the Vergilius Augusteus). After the 5th century the square capitals fell out of use, except as a display lettering for titles and chapter headings in conjunction with various script hands for body text, for example: uncial.