Mathnawi (مثنوي mathnawī) or masnavi (مثنوی Mas̲navī) is a kind of poem written in rhyming couplets, or more specifically "a poem based on independent, internally rhyming lines". Most mathnawī poems follow a meter of eleven, or occasionally ten, syllables, but had no limit in their length. Typical mathnawi poems consist of an indefinite number of couplets, with the rhyme scheme aa/bb/cc.
Mathnawī poems have been written in Persian, Arabic, Turkish, Kurdish and Urdu cultures. Certain Persian mat̲h̲nawī poems, such as Rumi's Masnavi-e Ma’navi, have had a special religious significance in Sufism. Other influential writings include the poems of Ghazali and ibn Arabi. Mathnawi's are closely tied to Islamic theology, philosophy, and legends, and cannot be understood properly without knowledge about it. Contrarily to Western poetry, Mathnawis do not serve as mere literary entertainment, but might be regarded as a source for the religion's metaphysics.
Arabic mathnawi poetry, also known as muzdawidj (مزدوج, literally "doubled," referring to the internal rhyme scheme of the lines), emerged and was popularized during the Abbasid era. Unlike the older poetic styles in Arabic, mathnawi verses are not monorhymes. Instead, they include an internal rhyme scheme within each bayt with an extensive use of alliteration and follow a specific meter. Arabic mathnawi (or muzdawidj) poetry is very similar to the Persian, Urdu, and Turkish equivalents, though with one major difference: most muzdawidj poems follow an aaa/bbb/ccc pattern, while the other mathnawi poems follow an aa/bb/cc pattern.
In Persian masnawī (مثنوى), the poems strictly adhere to a meter of 11 syllables, occasionally ten. While the length of a masnawī is not prescribed and is therefore unlimited, most of the better known masnawī are within a range of 2,000–9,000 bayts (verses). The first known masnawī poem was written in the Sāmānid period (4th/10th century).