Basīṭ (Arabic: بسيط) or al-basīṭ (البسيط), is a metre used in classical Arabic poetry. The word literally means "extended" or "spread out" in Arabic. Along with the ṭawīl, kāmil, and wāfir, it is one of the four most common metres used in pre-Islamic and classical Arabic poetry.

The metrical form of the basīṭ is often as follows (where "–" is a long syllable, "u" is a short syllable, and "x" is anceps, i.e., a syllable which can be either long or short):

The mnemonic words (tafāʿīl) used by Arab prosodists to describe this metre are: Mustafʿilun Fāʿilun Mustafʿilun Faʿilun (مُسْتَفْعِلُنْ فَاعِلُنْ مُسْتَفْعِلُنْ فَعِلُنْ).

The metre is usually used in couplets of eight feet each.

An example is the qasīda by al-Mutanabbi (915–965): “The poet reproaches Sayf al-Dawla” (king of Aleppo), a poem of 38 couplets, from which come the following well-known verses:

Although in the poem of al-Mutanabbi quoted above, the last foot of each half-verse is always | u u – |, other poets use the metre in the following form, where "uu" represents a biceps element, i.e. one where the two short syllables can optionally be replaced by one long one.

An example is the following drinking-song by Abu Nuwas which begins:

The metre also exists in a trimeter form of which the half-verse is as follows: