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

Square capitals were most often used to write the Roman alphabet in inscriptions, and less frequently in everyday handwriting. (The usual handwriting script in ancient Rome was Roman cursive.) Two of the most notable examples of square capitals used for inscriptions are the Pantheon and Trajan's Column, both in Rome. The script is characterized by sharp, straight lines, and, when executed correctly, gentle curves in the appropriate letters (O, P, C, etc.). It is also a serifed script. It is not technically a majuscule script, because there was no minuscule equivalent.

In the early Middle Ages, from around 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 script (the Vergilius Augusteus). After the 5th century, the script fell out of use, except when used as a display script, that is, used to write titles and chapter headings while another script, often uncial, was used for the rest of the text.