A poet of some celebrity, was the only son of Sir John Denham, Knight, of Little Horsley, in Essex, (some time chief baron of the exchequer in Ireland, and one of the lords justices of that kingdom,) by Eleanor, daughter of Sir Garnet More, Knight, Baron of Mellefont, in Ireland, and was born in Dublin in the year 1615; but was brought over from thence, two years afterwards, on his father being  made one of the barons of the exchequer in England, and received his education in London. In 1631, he was entered a gentleman commoner of Trinity College, Oxford, being then sixteen years of age; when, as Wood expresses it, “being looked upon as a slow and dreaming young man by his seniors and cotemporaries, and given more to cards and dice than his study, they could never then, in the least imagine, that he could ever enrich the world with his fancy, or issue of his brain, as he after-wards did.” He pursued his studies for three years at the university; and having undergone a public examina¬tion for bis degree of bachelor of arts, he entered himself at Lincoln’s Inn, with a view of studying the law. But notwithstanding his application to the object of his pursuit, he did not lose his propensity to cards and dice, and consequently became the dupe of the barpies tbat infest gaming tables. His father being informed of this, severely reproved him for his folly, and threatened to disinherit him if he did not reform. On this declaration be pro-fessed himself reclaimed, and, to testify the sincerity of his repentance, he wrote and published An Essay upon Gaming, which he presented to his father. But no sooner did his father die, than vice re-assumed her empire in his heart, and he returned to the gaming table loaded with several thousand pounds, which he was speedily un encumbered of.
 In 1641, he presented to the world his tragedy of the “Sophy,” which was greatly admired, and amongst others, by Waller, who took occasion to say of the author, that “he broke out like the Irish rebellion, threescore thousand strong, when nobody was aware or in the least suspected it.” Soon after be was pricked high sheriff of Surrey, and made governor of Farnham castle for the king; but not being skilled in military affairs, he soon resigned his post, and went to bis majesty’s court at Oxford; when, in 1643, he published his most celebrated poem, “Cooper’s Hill”; “a work,” says Dr. Johnson, that confers upon him the, rank and dignity of an original author.” Dryden likewise praises Cooper’s Hill very highly, and says, “ it is a poem, which for majesty of style, is, and ever will be, the standard of good writing.” Pope has also celebrated this poem in his “Windsor Forest” and it is so universally thought so much superior to his other poems, that some have suspected him, (though without any just foundation) not to have been the author of it. And in the “Session of the Poets,” printed in Dryden’s Miscellanies, we have the following insinuation :—

In 1647; the distresses of the royal family obliged him to relinquish the study of poetry, and engage in a more dangerous employment. He was entrusted by the queen with a message to the king, who was then in the hands of the army, and to whom he got admittance by the assistance of his acquaintance Hugh Peters, “ which trust,” says he, in the dedication of his poems to Charles II. “I performed with great safety to the persons with whom we corresponded; but, about nine months after, being discovered by their knowledge of Mr. Cowley’s hand, I happily escaped both for myself and them.”
He was, however, engaged in a greater undertaking, as, according to the authority of Wood, he conveyed away James Duke of York into France, in April 1648; but Clarendon declares to the contrary, and assures us, that the duke went off with Colonel Bamfield only, who contrived the means of escape. This year (1648) he published his translation of " Cato Major.”  Not long after, he was sent ambassador from Charles II. to the king of Poland, and William, (afterwards) Lord Crofts, was joined in the embassy with him. Among his poems is a ballad, entitled, “On my Lord Crofts’s and my Journey into Poland, from whence we brought 10,000£ for his Majesty, by the decimation (or tithing) of his Scottish subjects there.” About 1652, he returned to England, and the remnant pf his estate that the wars and the gamesters had left him, was sold by order of the parliament, and he was hospitably entertained by Lord Pembroke, at Wilton; but how he employed or supported himself till the Restoration, does not appear. After that event, he obtained the office of surveyor of the king’s buildings; and at the coronation of his majesty, was dignified with the order of Knight of the Bath. Wood pretends, that Charles I had granted our poet the reversion of that place after the decease of Inigo Jones, who held it; but Sir John himself, in the dedication of his poems, assures us, King Charles II. at his departure from St. Germains to Jersey, was pleased, freely, without his asking it, to confer it upon him. After the Restoration he composed his poem on Prudence and Justice; but shortly after he abandoned the study of poetry, and “made it his business,” he says, “ to draw such others as might be more serviceable to bis majesty, and, he hoped, more lasting.” It might be reasonably imagined that the favour of his sovereign and the esteem of the public, would now render him happy; but alas!  human felicity is short and uncertain. A second marriage brought upon him so much disquiet, that he had the misfortune to be deprived of his reason; and Dr. Johnson asserts, that when our poet was thus afflicted, Butler lampooned him for his lunacy, for which the doctor has inflicted on him a well-merited castigation. This malady was of short continuance, nor does his mind appear to have been impaired by it; as he wrote immediately after his recovery, his fine verses on the death of Cowley.
But poets themselves must fall like those they sing and he soon followed to the grave the subject of his panegyric, dying at his office (which an accurate biographer informs us had been built by himself, near Whitehall, on the 10th of March, 1688, and was interred in Westminster Abbey, near Chaucer, Spencer [sic], and Cowley, sharing the honours of their sepulchre, if not of their immortality.
 His works have been several times printed together in one volume, under the title of “Poems and Translations, with the Sophy, a tragedy”. Most of the occasional serious poems of Denham possess the merit of some ingenious thoughts and emphatical expressions, but cannot be mentioned as first-rate compositions.