Endymion is a poem by John Keats first published in 1818. Beginning famously with the line "A thing of beauty is a joy for ever", Endymion, like many epic poems in English (including John Dryden's translations from Virgil and Alexander Pope's translations from Homer), is written in rhyming, or 'heroic', couplets. Keats based the poem on the Greek myth of Endymion, the shepherd who falls in love with the moon goddess Selene. The poem elaborates on the original story and renames Selene "Cynthia" (an alternate name for Artemis).
Endymion received scathing criticism after its release, and Keats himself noted its diffuse and unappealing style (see, for example, The Quarterly Review April 1818 pp. 204-208; John Gibson Lockhart, Blackwood's Edinburgh Magazine August 1818). However, he did not regret writing it, as he likened the process to leaping into the ocean to become more acquainted with his surroundings; in a poem to Haydon, he expressed that "I would sooner fail than not be among the greatest."
Not all critics disliked the work. The poet Thomas Hood wrote 'Written in Keats' Endymion',in which the "Muse..charming the air to music...gave back Endymion in a dreamlike tale". Henry Morley said, "The song of Endymion throbs throughout with a noble poet's sense of all that his art means for him. What mechanical defects there are in it may even serve to quicken our sense of the youth and freshness of this voice of aspiration."