The rhyme royal stanza consists of seven lines, usually in iambic pentameter. The rhyme scheme is a-b-a-b-b-c-c. In practice, the stanza can be constructed either as a tercet and two couplets (a-b-a, b-b, c-c) or a quatrain and a tercet (a-b-a-b, b-c-c). This allows for a good deal of variety, especially when the form is used for longer narrative poems and along with the couplet, it was the standard narrative metre in the late Middle Ages.
Chaucer first used the rhyme royal stanza in his long poems Troilus and Criseyde and Parlement of Foules. He also used it for four of the Canterbury Tales including the Prioress' Tale and in a number of shorter lyrics. He may have adapted the form from a French ballade stanza or from the Italian Ottava rima, with the omission of the fifth line.
James I of Scotland used rhyme royal for his Chaucerian poem The Kingis Quair, and it is believed that the name of the stanza derives from this royal use. English and Scottish poets were greatly influenced by Chaucer in the century after his death and most made use of the form in at least some of their works. John Lydgate used the stanza for many of his occasional and love poems. The Scottish poet Robert Henryson consistently used the stanza throughout his two longest works, the Morall Fabillis and Testament of Cresseid, while the anonymous The Flower and the Leaf is another early use of the form. In the 16th century Thomas Wyatt used it in his poem They flee from me that sometime did me seek, Thomas Sackville in the Induction to The Mirror for Magistrates, Alexander Barclay in his Ship of Fools and Stephen Hawes in his Pastime of Pleasure.
The seven-line stanza began to go out of fashion during the Elizabethan era but it was still used by John Davys in Orchestra and by William Shakespeare in The Rape of Lucrece. Edmund Spenser wrote his Hymn of Heavenly Beauty using rhyme royal but he also derived his own Spenserian stanza with the rhyme scheme a-b-a-b-b-c-b-c-c partly by adapting rhyme royal. Like many stanzaic forms, rhyme royal fell out of fashion during the Restoration, and has never been widely used since. However, William Wordsworth employed rhyme royal (slightly modified by an alexandrine in the seventh line) in "Resolution and Independence," and notable twentieth-century poems in the stanza are W. H. Auden's Letter to Lord Byron (as well as some of the stanzas in The Shield of Achilles) and W. B. Yeats's A Bronze Head.
Here is the opening stanza of Troilus and Criseyde:
and this is the first stanza of the Wyatt poem: