- For etymology and similar terms see Octave.
Ottava rima is a rhyming stanza form of Italian origin. Originally used for long poems on heroic themes, it later came to be popular in the writing of mock-heroic works. Its earliest known use is in the writings of Giovanni Boccaccio.
The ottava rima stanza in English consists of eight iambic lines, usually iambic pentameters. Each stanza consists of three alternate rhymes and one double rhyme, following the a-b-a-b-a-b-c-c pattern. The form is similar to the older Sicilian octave, but evolved separately and is unrelated. The Sicilian octave is derived from the medieval strambotto and was a crucial step in the development of the sonnet, whereas the ottava rima is related to the canzone, a stanza form.
Boccaccio used ottava rima for a number of minor poems and, most significantly, for two of his major works, the Teseide (1340) and the Filostrato (1347). These two poems defined the form as the main one to be used for epic poetry in Italian for the next two centuries. For instance, ottava rima was used by Poliziano and by Boiardo in his 1486 epic poem Orlando Innamorato. The following year, Luigi Pulci published his Morgante Maggiore in which the mock-heroic, half-serious, half-burlesque use of the form that is most familiar to modern English-language readers first appeared. However, poets such as Ludovico Ariosto and Torquato Tasso continued to use ottava rima for serious epic poetry. It was later used in Italian libretti; perhaps the most famous example ends with the title of the comic opera Così fan tutte (1789).
In English, ottava rima first appeared in Elizabethan translations of Tasso and Ariosto. However, the form did not become popular for original works, and a section of William Browne's Britannia's Pastorals is the only known original work in the form that survives. The first English poet to write mock-heroic ottava rima was John Hookham Frere, whose 1817-8 poem Prospectus and Specimen of an Intended National Work used the form to considerable effect. Lord Byron read Frere's work and saw the potential of the form. He quickly produced Beppo, his first poem to use the form. Shortly after this, Byron began working on his Don Juan (1819–1824), probably the best-known English poem in ottava rima. Byron also used the form for The Vision of Judgment (1822). Shelley translated the Homeric Hymns into English in ottava rima. In the 20th century, William Butler Yeats used the form in several of his best later poems, including "Sailing to Byzantium" and "Among School Children". So did Kenneth Koch for instance in his autobiographical poem "Seasons on Earth" of 1987.
Outside of Italian and English, ottava rima has not been widely used, although the Spanish poets Boscan, Alonso de Ercilla y Zúñiga and Lope de Vega all experimented with it at one time or another. It is also the meter of several medieval Yiddish epic poems, such as the Bovo-Bukh (1507–1508), which were adaptations of Italian epics. In Russia, Pavel Katenin instigated a high-profile dispute on the proper way of translating Italian epics, which resulted in Alexander Pushkin's ottava rima poem "The Little House in Kolomna" (1830), which took its cue from Lord Byron's Beppo. Pushkin's poem opens with a lengthy tongue-in-cheek discussion of the merits of ottava rima. Luís de Camões's 16th-century epic Os Lusíadas, the most important work in the Portuguese language, is entirely written in ottava rima.
Some examples 
But chiefly, when the shadowy moon had shed
O'er woods and waters her mysterious hue,
Their passive hearts and vacant fancies fed
With thoughts and aspirations strange and new,
Till their brute souls with inward working bred
Dark hints that in the depths of instinct grew
Subjection not from Locke's associations,
Nor David Hartley's doctrine of vibrations.
"Go, little book, from this my solitude!
I cast thee on the waters – go thy ways!
And if, as I believe, thy vein be good,
The world will find thee after many days."
When Southey's read, and Wordsworth understood,
I can't help putting in my claim to praise –
The four first rhymes are Southey's every line:
For God's sake, reader! take them not for mine.
He thought he was a kind of living myth
And hence deserving of ottava rima,
The scheme that Ariosto juggled with,
Apt for a lecherous defective dreamer.
He'd have preferred a stronger-muscled smith,
Anvilling rhymes amid poetic steam, a
Sort of Lord Byron. Byron was long dead.
This poetaster had to do instead.