Il Penseroso is a poem by John Milton, first found in the 1645/1646 quarto of verses The Poems of Mr. John Milton, both English and Latin, published by Humphrey Moseley. It was presented as a companion piece to L'Allegro, a vision of poetic mirth. The speaker of this reflective ode dispels "vain deluding Joys" from his mind in a ten-line prelude, before invoking "divinest Melancholy" to inspire his future verses. The melancholic mood is idealised by the speaker as a means by which to "attain / To something like prophetic strain," and for the central action of Il Penseroso – which, like L'Allegro, proceeds in couplets of iambic tetrameter – the speaker speculates about the poetic inspiration that would transpire if the imagined goddess of Melancholy he invokes were his Muse. The highly digressive style Milton employs in L'Allegro and Il Penseroso dually precludes any summary of the poems' dramatic action as it renders them interpretively ambiguous to critics. However, it can surely be said that the vision of poetic inspiration offered by the speaker of Il Penseroso is an allegorical exploration of a contemplative paradigm of poetic genre.

John Milton was an English poet, polemicist, and civil servant. His 1667 epic poem Paradise Lost, written in blank verse and including twelve books, was written in a time of immense religious flux and political upheaval. It addressed the fall of man, including the temptation of Adam and Eve by the fallen angel Satan and God's expulsion of them from the Garden of Eden. Paradise Lost elevated Milton's reputation as one of history's greatest poets. He also served as a civil servant for the Commonwealth of England under its Council of State and later under Oliver Cromwell.