What is the title of the poem by John Keats that begins with "A thing of beauty is a joy forever"?

The poem that begins with the line "A thing of beauty is a joy forever" is titled "Endymion." This opening line encapsulates one of the central themes of the poem, which explores the enduring nature of beauty and the deep emotional response it invokes. "Endymion" is an expansive narrative poem that draws on the myth of Endymion, a beautiful youth who is loved by the moon goddess Selene.

The significance of this opening line lies in its assertion that true beauty provides lasting joy, suggesting a philosophical perspective that beauty transcends the temporary nature of life. The poem reflects Keats' Romantic ideals, encapsulating the belief that beauty is not only found in the physical realm but also in experiences and the imagination.

The other options, while notable works by Keats, do not begin with this specific line. "Ode to a Nightingale" focuses on themes of nature and mortality; "Hyperion" addresses themes of power and change; and "La Belle Dame sans Merci" explores themes of love and loss. Each of these poems has its own distinct subject matter and tone, but none share the opening of "Endymion."