A prosimetrum (plural prosimetra) is a poetic composition which exploits a combination of prose (prosa) and verse (metrum); in particular, it is a text composed in alternating segments of prose and verse. It is widely found in Western and Eastern literature. While narrative prosimetrum may encompass at one extreme a prose story with occasional verse interspersed, and at the other, verse with occasional prose explanations, in true prosimetrum the two forms are represented in more equal measure. A distinction is sometimes drawn between texts in which verse is the dominant form and those in which prose dominates; there the terms prosimetrum and versiprose are applied respectively.
The term prosimetrum is first attested in the Rationes dictandi of Hugh of Bologna, in the early 12th century. Sources differ on the date, one suggesting around 1119, another about 1130. Hugh divided metrical composition into three kinds: quantitative verse (carmina), verse based on syllable count and assonance (rithmi), and "the mixed form ... when a part is expressed in verse and a part in prose" (prosimetrum). The derived adjective prosimetrical occurs in English as early as Thomas Blount’s Glossographia (1656) where it is defined as "consisting partly of Prose, partly of Meteer or Verse".
Works such as historical chronicles and annals, which quote poetry previously composed by other authors, are not generally regarded as "true" prosimetra. In the Old Norse-Icelandic tradition, however, vernacular histories and family sagas that quote verses by other authors are commonly accepted as prosimetra. Quoted or "inset" verses are a familiar feature of longer historical texts in the Old Irish and Middle Irish traditions as well. The role of such verse quotations within the prose narrative varies; they may be mined as historical source-material, cited as factual corroboration of an event or recited by a character as dialogue.