Denham, Sir John (1559–1639), judge, was born probably in London, second son of William Denham – a goldsmith of St Matthew's, Friday St., London, who later settled in Thorpe, Surrey – and his wife Joan. Having been a member of Furnival's Inn, Denham entered Lincoln's Inn on 19 August 1577 and was called to the bar on 29 June 1587. In Lent 1607 he was elected reader of Lincoln's Inn, and he became sergeant-at-law in the spring of 1609. By then he was counsel for and steward of Eton college. On 4 July 1609 he was appointed chief baron of the exchequer in Ireland, knighted, and made a member of the Irish privy council.
He travelled in the same year to Ireland, where he was immediately preoccupied with bringing the Irish exchequer's practices into line with those of its English counterpart. The Dublin administration was then heavily in debt, but he appears to have had success in increasing revenues, particularly from customs. He also appears as justice of the assize from 1611 onwards, generally riding the Leinster circuit. He complained of the power and judicial privileges of certain noblemen, which prevented people from turning to the king's courts for justice. On 28 April 1612 he was raised to the post of chief justice of the king's bench. During his time in Ireland he impressed and gained the confidence of Sir Arthur Chichester (qv), lord deputy of Ireland 1605–15, who in May 1613 sent Denham and two others to London to defend the Dublin government from the criticisms of catholic MPs in the Irish parliament. He returned to Dublin on 31 August 1614. Between November 1615 and July 1616, he served as lord justice of Ireland, following Chichester's dismissal. As such, he continued Chichester's judicial onslaught against catholicism by prosecuting jurors for failing to present recusants in Westmeath and Longford, and by fining civic officials for not taking the oath of supremacy. As before, these measures met with determined legal and extra-legal opposition from prominent catholic lawyers, merchants, and landowners.
In 1617 Denham left Ireland, having acquitted himself well during his years of service, to become baron of the exchequer in England. He continued to advise the crown on Irish matters, and on 9 May 1623 he was appointed to the newly created commission of Irish affairs. In England he established himself at Egham, Surrey, and served as a judge until his death on 6 January 1639. He was buried in Egham, where there is a monument to his memory.
He married first Cicely (d. 1612), daughter of Richard Kellefert, and then (c.1614) Eleanor, daughter of Garret Moore (qv), Viscount Drogheda. With his second wife, who died in childbirth in 1619, he had his only child, the wayward royalist poet John Denham (qv).