Cassius Longinus (c. 213-273 AD, who lived and worked mainly inAlexandria, was one of the more renowned philologists of the third century. He wrote an Art of Rhetoric, lectured on Plato, and is athor of several grammatical and rhetorical fragments. He was a teacher of Porphyry and mentioned in Porphyry's Life of Plotinus.

The manuscript of Peri Hupsous, or On the Sublime, is attributed to one Dionysius or Longinus. Scholars have made an attempt to identify the Longinus of the manuscript with Cassius Longinus but the attribution is uncertain. In the 18th century, most scholars favoured attribution to Cassius Longinus, but the attributiong gradually fell out of favour due to concerns that some of the vocabulary of Peri Hupsous and some of the rhetorical theories seem incompatible with extant works of Cassius Longinus. Most recently, Malcolm Heath has argued that the case against identification of Longinus with the author of On the Sublime is weak. In terms of the concept of sublimity itself, the idea would fit well with what we know of evolving Platonizing concepts of reading and authorship, something whic suggests we should seriously consider Cassius Longinus as the author.