Reynolds was born in Shrewsbury to George Reynolds, teacher at Shrewsbury School and Charlotte Cox Reynolds. His mother was related to the Hamilton family, from which Reynolds received his middle name, which included the Gothic writer William Thomas Beckford. Reynolds attended Shrewsbury School, then enrolled at St Paul's School in London,^[3] when the family moved in 1806, completing formal education in 1810.

He took a junior clerkship in an insurance office, the Amicable Society for Perpetual Assurance, working there at least until 1816; and from 1818 to 1820, he worked in Essex Street for Francis Fladgate, a solicitor.^[4] Meanwhile, he pursued his self-education by reading widely in classical and English literature and also began writing poetry. He was encouraged in his literary interests by his friend John F M Dovaston, a former student of Reynolds's father.

Reynolds's first published poem, "Ode to Friendship" appeared in the Gentleman's Magazine in 1812. He was a prolific journalist and reviewer, and published collections of poems and a diverse array of articles. He received favourable notice from a number of critics and poets, including Byron, whose work Reynolds had closely imitated. Later he published The Eden of Imagination, imitating Wordsworth, who had also encouraged him. Early in his poetic career, John Clare claimed to be a huge admirer of Reynolds's work, and the two met and socialised with other contributors to the London Magazine. In addition to the latter, Reynolds also contributed to the Edinburgh Review during the 1820s and in 1831 he became part-owner of The Athenaeum.^[5]

His friend Leigh Hunt supported his writing and introduced him to another young poet Hunt greatly admired, the then unknown John Keats. Together with Percy Bysshe Shelley, the two were featured by Hunt in his 1816 article on a “new school of poets”, called ‘’Young Poetry’’.^[6] Keats and Reynolds became friends, encouraging and challenging each other in their quest for literary recognition. Keats was in 1819 to praise Reynolds’ Wordsworth parody, ‘’Peter Bell: A Lyrical Ballad’’;^[7] and it is in witty parody that Reynolds is now considered to have been at his poetic best.^[8]

In 1822, he married Eliza Drewe, which led to a friendship and literary collaboration with her brother-in-law, Thomas Hood. Together the two wrote several comic and satirical pieces, the most popular being Odes and Addresses to Great People in 1825.

Tragedy struck in 1835 when his ten-year-old daughter Lucy died. He was bankrupt in 1838 but continued earning a small income writing. In 1847 he moved to the Isle of Wight as assistant clerk in a county court. Reynolds became depressed and started drinking heavily, although he was not without friends and admirers to the end. In 1852, Reynolds was found dead in the bedroom of his father's apartment in Newport, three months after his birthday.

• Zetosophian society

• Barnard, John, Keats’s ‘Robin Hood’, John Hamilton Reynolds, and the ‘Old Poets’. Warton Lecture on English Poetry; published in Proceedings of the British Academy, Vol. 75.
• Gittings, Robert, The Poetry of John Hamilton Reynolds. In: Ariel, Vol. I, No. 4. October 1970.
• Hudnall, Clayton E., John Hamilton Reynolds, James Rice, and Benjamin Bailey in the Leigh Browne-Lockyer Collection. In: Keats-Shelley Journal, Vol. XIX, 1970, pp. 11–39.
• Jones, Leonidas M., The Life of John Hamilton Reynolds. Hanover, University Press of New England. 1984.
• Jones, Leonidas M., New Letters, Articles, and Poems by John Hamilton Reynolds. In: Keats-Shelley Journal, Vol. VI, 1957, pp. 97–108.
• Jones, Leonidas M., Reynolds and Keats. In: Keats-Shelley Journal, Vol. VII, 1958, pp. 47–59.
• Jones, Leonidas M., Reynolds and Rice in Defence of Patmore. In: The Keats-Shelley Memorial Bulletin, No. XXI, 1970, pp. 12–20.
• Kaier, Anne, John Hamilton Reynolds: Four New Letters. In: Keats-Shelley Journal, Vol. XXX, 1981.
• Kovesi, Simon, John Hamilton Reynolds, John Clare and The London Magazine, The Wordsworth Circle, 42.3 (Summer 2011), 226-235.
• Kaufman, Paul, The Reynolds-Hood Commonplace Book: A Fresh Appraisal. In: Keats-Shelley Journal, Vol. X, Winter 1961.
• McMullin, B.J., John Hamilton Reynolds and Archibald Constable & Co., 1819-1821. In: Keats-Shelley Journal, 1994, pp. 19–24.
• Mann, Phyllis G., The Reynolds Family. In: Keats-Shelley Journal, Vol. V, Winter 1956.
• Marsh, George L., New Data on Keats's Friend Reynolds. In: Modern Philology, Vol. XXV, No. 3. February 1928.
• Morgan, Peter F., John Hamilton Reynolds and Thomas Hood. In: Keats-Shelly Journal, Vol. XI, 1962.
• Pope, Willard B., John Hamilton Reynolds, the Friend of Keats. Reprint from Wessex, 1935.
• Reynolds, John Hamilton (Ed. Leonidas M. Jones), Selected Prose of John Hamilton Reynolds. Cambridge, Harvard University Press. 1966.
• Reynolds, John Hamilton (Ed. Leonidas M. Jones), The Letters of John Hamilton Reynolds. Lincoln, University of Nebraska. 1973.
• Richardson, Joanna, Letters from Lambeth. The correspondence of the Reynolds family with John Freeman Milward Dovaston 1808-1815. Woodbridge, Boydell. 1981.

• National Portrait Gallery
• Portraits of John Hamilton Reynolds at the National Portrait Gallery, London  
• "Archival material relating to John Hamilton Reynolds". UK National Archives.  
• Headstone in Church Litten, Newport, Isle of Wight
• Works by John Hamilton Reynolds at the Internet Archive