On the Sublime is a Roman-era Greek work of literary criticism dated to the 1st century AD. Its author is unknown, but is conventionally referred to as Longinus (/lɒnˈdʒaɪnəs/; Ancient Greek: Λογγῖνος Longĩnos) or Pseudo-Longinus. It is regarded as a classic work on aesthetics and the effects of good writing. The treatise highlights examples of good and bad writing from the previous millennium, focusing particularly on what may lead to the sublime.

The author's identity has been debated for centuries. The oldest surviving manuscript, from the 10th century, indicates the original author was named "Dionysius or Longinus", which was later misread as "Dionysius Longinus". Subsequent interpretations have attributed the work to Dionysius of Halicarnassus (1st century) or Cassius Longinus (c. 213–273 AD), though neither is now widely accepted.