Prose poetry is prose that breaks some of the normal rules of prose discourse for heightened imagery or emotional effect.
As a specific poetic form, prose poetry was originated in the 19th century in France. French prose was governed by laws so strict that by breaking them, it was possible to create prose that was seen to be intended as poetry. Poets such as Charles Baudelaire, Arthur Rimbaud, and Stephane Mallarmé were among the founders of the form.
It used to be said that prose poetry was impossible in English, because the English language was not so strictly governed by rules as the French was. In the twentieth century, when English prose has become more and more governed by the iron laws of Strunk and White, this may no longer be the case. Rapturous, rhythmical, and image-laden prose from previous centuries, such as is found in Jeremy Taylor or Thomas de Quincey, strikes 21st century readers as having something of a poetic quality. Much contemporary poetry is written in free verse, and the difference between much free verse and prose poetry may be more in the typography than in the content.