Alastor, or The Spirit of Solitude

Alastor, or The Spirit of Solitude is a poem by Percy Bysshe Shelley, written from 10 September to 14 December in 1815 in Bishopsgate, near Windsor Great Park and first published in 1816. The poem was without a title when Shelley passed it along to his contemporary and friend Thomas Love Peacock. The poem is 720 lines long. It is considered to be one of the first of Shelley's major poems.

Peacock suggested the name Alastor, which comes from Roman mythology. Peacock has defined Alastor as "evil genius". The name does not refer to the hero or Poet of the poem, however, but instead to the spirit who divinely animates the Poet's imagination.