A caesura (/sɪˈzjʊərə/, pl. caesuras or caesurae; Latin for "cutting"), also written cæsura and cesura, is a metrical pause or break in a verse where one phrase ends and another phrase begins. It may be expressed by a comma (,), a tick (✓), or two lines, either slashed (//) or upright (||). In time value, this break may vary between the slightest perception of silence all the way up to a full pause.

In classical Greek and Latin poetry a caesura is the juncture where one word ends and the following word begins within a foot. In contrast, a word juncture at the end of a foot is called a diaeresis. Some caesurae are expected and represent a point of articulation between two phrases or clauses. All other caesurae are only potentially places of articulation. The opposite of an obligatory caesura is a bridge where word juncture is not permitted.

In modern European poetry, a caesura is defined as a natural phrase end, especially when occurring in the middle of a line. A masculine caesura follows a stressed syllable while a feminine caesura follows an unstressed syllable. A caesura is also described by its position in a line of poetry: a caesura close to the beginning of a line is called an initial caesura, one in the middle of a line is medial, and one near the end of a line is terminal. Initial and terminal caesurae are rare in formal, Romance, and Neoclassical verse, which prefer medial caesurae.

In verse scansion, the modern caesura mark is a double vertical bar ⟨||⟩ or ⟨${\displaystyle \|}$⟩, a variant of the single-bar virgula ("twig") used as a caesura mark in medieval manuscripts. The same mark separately developed as the virgule, the single slash used to mark line breaks in poetry.

Caesurae were widely used in Greek poetry. For example, in the opening line of the Iliad:

μῆνιν ἄειδε, θεὰ, || Πηληϊάδεω Ἀχιλῆος
mênin áeide, theà, || Pēlēïádeō Akhilêos
("Sing the rage, o goddess, || of Achilles, the son of Peleus.")

This line includes a masculine caesura after θεὰ, a natural break that separates the line into two logical parts. Homeric lines more commonly employ feminine caesurae; this preference is observed to an even higher degree among the Alexandrian poets. An example of a feminine caesura is the opening line of the Odyssey:

ἄνδρα μοι ἔννεπε, Μοῦσα, || πολύτροπον, ὃς μάλα πολλὰ
ándra moi énnepe, Moûsa, || polútropon, hòs mála pollà
("Tell me, Muse, of the man || of many wiles, who very much (wandered)")