Digression (παρέκβασις [parékbasis] in Greek; egressio, digressio or excursio in Latin) is a section of a composition or speech that marks a temporary shift of subject; the digression ends when the writer or speaker returns to the main topic. Digressions can be used intentionally as a stylistic or rhetorical device.

In classical rhetoric since Corax of Syracuse, especially in Institutio Oratoria of Quintilian, digression was a regular part of any oration or composition. After setting out the topic of a work and establishing the need for attention to be given, the speaker or author would digress to a seemingly disconnected subject before returning to a development of the composition's theme, a proof of its validity, and a conclusion. A schizothemia (from Ancient Greek σχῐ́ζωθέμία, lit. 'split discussion') is a digression by means of a long reminiscence.

Cicero was a master of digression, particularly in his ability to shift from the specific question or issue at hand (the hypothesis) to the more general issue or question that it depended upon (the thesis). As was the case with most ancient orators, Cicero's apparent digression always turned out to bear directly upon the issue at hand. During the Second Sophistic (in Imperial Rome), the ability to guide a speech away from a stated theme and then back again with grace and skill came to be a mark of true eloquence.

The term "digression" comes from the Latin word digressio: "a going away, departing," noun of action from past participle stem of digredi "to deviate", from dis- "apart, aside" + gradi "to step, go".

Digressions in a literary text serve a diverse array of functions, such as a means to provide background information, a way to illustrate or emphasize a point through example or anecdote, and even a channel through which to satirize a subject.

In 800-500 BCE, Homer relies upon digression in his composition of The Iliad in order to provide his audience with a break from the primary narrative, to offer background information, and, most importantly, to enhance the story's verisimilitude. Through these digressions Homer ensures his audience's devotion to the characters and interest in the plot.

For example, in Book Eleven, Homer employs a mini-digression when Agamemnon comes upon brothers Peisandros and Hippolokhos in battle. After they come to Agamemnon as suppliants, he remembers that their father was one who denied Menelaos’ emissaries and “held out for killing [them] then and there”. This short interlude from the action provides the audience with a critical fact about the beginning of the war and the nature of the opposing parties.

In 18th-century literature, the digression (not to be confused with subplot) was a substantial part of satiric works. Works such as Jonathan Swift's A Tale of a Tub, Laurence Sterne's Tristram Shandy and Diderot's Jacques le fataliste et son maître even made digressiveness itself a part of the satire. Sterne's novel, in particular, depended upon the digression, and he wrote, "Digressions, incontestably, are the sunshine; — they are the life, the soul of reading; — take them out of this book (Tristram Shandy) for instance, — you might as well take the book along with them." This use of digression as satire later showed up in Thomas Carlyle's work.