A quatrain is a type of stanza, or a complete poem, consisting of four lines.

Existing in various forms, the quatrain appears in poems from the poetic traditions of various ancient civilizations including Ancient Greece, Ancient Rome, and China; and, continues into the 21st century, where it is seen in works published in many languages. During Europe's Dark Ages, in the Middle East and especially Iran, polymath poets such as Omar Khayyam continued to popularize this form of poetry, also known as Ruba'i, well beyond their borders and time. There are fifteen possible rhyme schemes, but the most traditional and common are: AAAA, ABAB, and ABBA.