Muwashshah (Arabic: مُوَشَّح muwaššaḥ 'girdled'; plural مُوَشَّحَات muwaššaḥāt; also تَوْشِيْح tawšīḥ 'girdling,' pl. تَوَاشِيْح tawāšīḥ) is a strophic poetic form that developed in al-Andalus in the late 10th and early 11th centuries. The muwaššaḥ, embodying the Iberian rhyme revolution, was the major Andalusi innovation in Arabic poetry, and it was sung and performed musically. The muwaššaḥ features a complex rhyme and metrical scheme usually containing five aghṣān (أَغْصَان 'branches'; sing. غُصْن ghuṣn), with uniform rhyme within each strophe, interspersed with asmāṭ (أَسْمَاط 'threads for stringing pearls'; sing. سِمْط simṭ) with common rhyme throughout the song, as well as a terminal kharja (خَرْجَة 'exit'), the song's final simṭ, which could be in a different language. Sephardic poets also composed muwaššaḥāt in Hebrew, sometimes as contrafacta imitating the rhyme and metrical scheme of a particular poem in Hebrew or in Arabic. This poetic imitation, called muʿāraḍa (مُعَارَضَة 'contrafaction'), is a tradition in Arabic poetry.

The kharja, or the markaz (مَـْركَز 'center') of the muwaššaḥ, its final verses, can be in a language that is different from the body; a muwaššaḥ in literary Arabic might have a kharja in vernacular Andalusi Arabic or in a mix of Arabic and Andalusi Romance, while a muwaššaḥ in Hebrew might contain a kharja in Arabic, Romance, Hebrew, or a mix.

The muwaššaḥ musical tradition can take two forms: the waṣla of the Mashriq and the Andalusi nubah of the Maghrib.

While the qasida and the maqama were adapted from the Mashriq, strophic poetry is the only form of Andalusi literature known to have its origins in the Iberian Peninsula. Andalusi strophic poetry exists in two forms: the muwaššaḥ: a more complex version in Standard Arabic with the exception of the concluding couplet, or the kharja, and zajal: a simpler form entirely in vernacular Arabic. The earliest known muwaššaḥs date back to the eleventh century.

It was exported to the east, and celebrated there by figures such as Ibn Sanāʾ al-Mulk and ibn Dihya al-Kalby. The corpus of muwaššaḥs is formed by pieces in Hebrew and Andalusi Arabic. Tova Rosen describes the muwaššaḥ as "a product and a microcosm of the cultural conditions particular to al-Andalus. The linguistic interplay between the standard written languages—Arabic and Hebrew—and the oral forms—Andalusi Arabic, Andalusi Romance, Hebrew, and other Romance languages—reflect the fluidity and diversity of the linguistic landscape of al-Andalus.

The earliest known source on the muwashshah is Ibn Bassam’s 'Dhakhīra fī mahāsin ahl al-Jazīra  [ar]'. He ascribes the invention of the muwashshah to the 10th century blind poet Muhammad Mahmud al-Qabri or ibn ‘Abd Rabbih. Nonetheless, there are no extant muwashshah poems attributed to these authors.

Ibn Sanāʾ al-Mulk (d. 1211), author of Dār aṭ-ṭirāz fī ʿamal al-muwashshaḥāt (دار الطراز في عمل الموشحات), wrote the most detailed surviving musical description of the muwashshaḥ. He wrote that some of the muwashshaḥāt had lyrics that fit their melodies (sometimes through melisma), while others had improvised nonsense syllables to fill out the melodic line—a practice that survives to the present with relevant sections labeled as shughl (شُغل 'work') in songbooks.

Examples of muwaššaḥ poetry start to appear as early as the 9th or 10th century. It is believed to come from the Arabic root w-š-ḥ (وشح) which means any thing that a woman might wear on her neck from a necklace to a scarf, and the verb Tawašḥ means to wear. Some relate it to the word for a type of double-banded ornamental belt, the wišaḥ, which also means a scarf in Arabic. The underlying idea is that, as there is a single rhyme running through the refrain of each stanza, the stanzas are like objects hung from a belt.