Henry Samuel Chapman was born in Kennington, London, England, on 21 July 1803, the son of Henry Chapman, a civil servant in the Barrack Department, and his wife, Ann Hart Davies. He was educated in schools at Bromley, Kent, and at London. His career began in banking in London but he travelled on business, spending the winter in Amsterdam in 1822 and acquiring facility in Dutch and German. At the age of 19 he was sent by his employer to Quebec. For the next 10 years he was moderately successful in business. In 1833 he met Samuel Revans and began an association which was continued later in New Zealand. They founded the Daily Advertiser in Montreal, the first daily newspaper in Canada, supporting French aspirations and the cause of responsible self-government. The paper was influential but not financially successful and lasted only a year.
Chapman returned to England in 1835 and became involved in liberal and radical causes. He was the paid agent of the Liberal party of Canada in England, which supported J. A. Roebuck and Louis-Joseph Papineau. Agitation by the party led to the Durham Report in 1839. Pamphleteering and journalism kept Chapman busy, supporting such causes as the Anti-Corn Law League and free trade, in which he was closely associated with such influential leaders as Richard Cobden, J. S. Mill, J. L. Ricardo, Charles Buller, Francis Place, and with E. G. Wakefield and Dr G. S. Evans. He also served on several royal commissions, including one investigating the Yorkshire wool industry, and he contributed the article on wool and woollen manufacturing to the seventh edition of the Encyclopaedia Britannica.
In the late 1830s Chapman read for the Bar. He was admitted to the Middle Temple in London on 12 June 1840. Six days before, on 6 June 1840, he had married Catherine Brewer at the church of St Marylebone, London. There were seven children of the marriage.
In February 1840, under the influence of E. G. Wakefield, Chapman began publishing the New Zealand Journal as proprietor-editor. The newspaper was the unofficial organ of the New Zealand Company, which subsidised it. It was published fortnightly for the next three years. During this period Chapman wrote several treatises advocating responsible government for New Zealand, published collectively as The New Zealand portfolio in 1843. Chapman's interest in New Zealand led in 1843 to his appointment by Lord Stanley, secretary of state for the colonies, as judge of the Supreme Court of New Zealand for the southern district, which included Wellington, Nelson, New Plymouth and later Christchurch. He was the first puisne judge in New Zealand.
With his wife, whose health was of some concern, and a two-year-old son, Henry, Chapman arrived in Auckland on 23 December 1843 on the Bangalore. Captain Robert FitzRoy was on the same ship on his way to take up the governorship of New Zealand, and they both took their oaths of office in Auckland on 26 December 1843. Chapman settled in Wellington, at Karori. His residence, Homewood, was based on a 'beautiful design' by the English architect Thomas Allom, and was built by Samuel Duncan Parnell. Chapman presided over the Court in Wellington, but also travelled by government brig to sessions in New Plymouth and Christchurch. He was obliged to walk long distances when no transport was available. During his term of office he assisted Chief Justice William Martin in preparing a report on Supreme Court procedure for New Zealand, which was the forerunner of the present code.
In 1851 Charlotte Godley wrote of Chapman, 'He has a great big faded-looking head, with bristling grey hair, spectacles and a lame foot'. She admired his cleverness but disliked him and found his children objectionable: 'he talks, Oh! so grandly – plainly telling you that he considers himself too good for his present position'.
In January 1852, unexpectedly, Chapman was offered the position of colonial secretary of Van Diemen's Land (Tasmania), which he promptly accepted. Released from the constraints of a position in the judiciary, he was soon involved in controversy. He followed local opinion and his own convictions in opposing further transportation of convicts, against the policy of the governor. He was dismissed by the Colonial Office but offered a governorship in the West Indies, which he refused. In 1854 he went to Melbourne to practise law. He entered politics, being elected to the Victorian Legislative Council in February 1855. He is remembered in Australia for his drafting of the first ballot legislation, which included what became known as the Victorian Ballot. For lengthy periods between 1857 and 1862 he was a member of the Legislative Council and an influential and active figure in government. He also lectured on law at Melbourne University and was the Melbourne correspondent of The Times of London. In 1862 he was appointed a temporary judge in the Supreme Court of Victoria.
In early 1864, in spite of his controversial record in Australia, Chapman was offered a post as judge of the Supreme Court in New Zealand. He accepted and returned to preside over the Court in Dunedin. Here he settled and was to remain for the rest of his life. In 1866 he lost his wife and three of his children; they were drowned in a shipwreck while returning from a visit to England. On 11 April 1868 at Avoca, Victoria, Australia, he married Selina Frances Carr. She was the sister-in-law of an old legal colleague. Family life was important to Chapman: he was a devoted father who provided good opportunities for his surviving children. One son, Frederick Revans (named after Chapman's old colleague), became a distinguished judge in New Zealand, and another son, Martin, founded the Wellington legal firm now called Chapman Tripp Sheffield Young.
As a Supreme Court judge Chapman was unable to engage in political affairs, but in private conversations and in correspondence his comments were trenchant and he showed intolerance towards many of his contemporaries. For instance, he described FitzRoy as 'ignorant' and 'thoroughly selfish', George Grey as insincere, and Edward Eyre as 'totally unfit' for his office. However, in his judicial capacity he maintained a sense of proportion and was respected for his deep understanding of legal matters and for his integrity.
Chapman was a music lover and had many scholarly interests. In particular, he possessed a wide knowledge of languages and philology. In Dunedin in 1876 he published Specimens of fossilised words; or obsolete roots embedded in modern compounds; with some old words with new meanings. This work was later recognised as a significant contribution to the study of linguistics. Chapman was a member of the council of the University of Otago from 1869 to 1881 and its chancellor from 1876 to 1879. He had progressive views on education: in August 1871 he presented to the council Learmonth Dalrymple's petition requesting admission of women to the university. His wife, Selina Chapman, was the first signatory to the petition.
After his retirement in 1875 Chapman pursued business interests, lent assistance to community projects and gave lectures on various subjects. He died at Dunedin on 27 December 1881, aged 78 years.