Isambard Kingdom Brunel (1806-1859), English engineer, only son of Sir M.I. Brunel, was born at Portsmouth on the 9th of April 1806. He displayed in childhood singular powers of mental calculation, great skill and rapidity as a draughtsman, and a true feeling for art. At the age of fourteen he was sent to Paris, to study at the Collège Henri Quatre. In 1823 he entered his father's office as assistant-engineer, just at the time when the project of the Thames Tunnel was beginning to take shape; and during the later portion of the time, from 1825, when the work was begun, till 1828, when it was stopped by an irruption of the river, he was both nominal and actual resident engineer. In November 1829 he sent in designs and plans for the projected suspension bridge over the Avon at Clifton, but in consequence of objections raised by Thomas Telford, the referee of the bridge committee, his plans were rejected. But a new design which he sent in on a second competition in 1831 was accepted, and he was appointed engineer.

The works were begun in 1836, but owing to lack of funds were not completed until 1864, after Brunel's death; his design, however, was closely adhered to, and the chains employed came from the old Hungerford suspension bridge (London), which he had built in 1841-1845, but which was displaced in 1862 by the Charing Cross railway bridge.

In March 1833 Brunel, at the age of twenty-seven, was appointed engineer of the newly-projected Great Western railway. For several years his energies were taxed to the utmost by the conflict with obstructive landowners and short-sighted critics; but he showed himself equal to the occasion, not only as a professional man, but as a persuasive negotiator. Among the engineering triumphs on that railway are the Hanwell viaduct, the Maidenhead bridge and the Box tunnel, at the time the longest in the world. The famous "battle of the gauges" took its rise from his introduction of the broad (7 ft.) gauge on that line. In 1846 he resigned his office as engineer of the Great Western railway. In 1844 he had recommended the adoption of the atmospheric system on the South Devon railway, but after a year's trial the system was abandoned. The last and greatest of Brunel's railway works was the Royal Albert bridge over the river Tamar at Saltash. This work, sanctioned by parliament in 1845, was constructed between 1853 and 1859.

In addition to the arduous labours of railway engineering Brunel took a leading part in the systematic development of ocean steam navigation. As early as October 1835 he had suggested to the directors of the Great Western railway, that they should "make it longer, and have a steamboat to go from Bristol to New York, and call it the 'Great Western.'" The project was taken up, and the "Great Western" steamship was designed by Brunel, and built at Bristol under his superintendence. It was much longer than any steamer of the day, and was the first steamship built to make regular voyages across the Atlantic. While the vessel was building a controversy was raised about the practicability of Brunel's scheme, Dr D. Lardner asserting dogmatically that the voyage could not be made, and backing his assertion with an array of figures. His view was widely accepted, but the work went on, and the voyage was accomplished in 1838. Brunel at once undertook a still larger design in the "Great Britain," which was the first large iron steamship, the largest ship afloat at that time, and the first large ship in which the screw-propeller was used.

She made her first voyage from Liverpool to New York in August and September 1845; but in the following year was carelessly run upon the rocks in Dundrum Bay on the coast of Ireland. After lying there nearly a year without material damage she was got off and was employed in the Australian trade. Brunel soon after began to meditate a still vaster project, the construction of a vessel large enough to carry all the coal required for a long voyage out, and if coal could not be had at the out port, then to carry enough also for the return voyage. It seemed to him, further, that a great increase of size would give many advantages for navigation. During his connexion as engineer with the Australian Mail Company he worked out into a practical shape his conception of a "great ship"; and in 1852 his scheme was laid before the directors of the Eastern Steam Navigation Company. It was adopted, the projector being appointed engineer, and after much time occupied about contracts and specifications the work was begun in December 1853. Immense difficulties in the progress of construction caused delays from time to time.

The operation of launching was several times attempted in vain; but at length the gigantic vessel, the "Great Eastern," was got afloat on the 31st of January 1858. Much remained to be done to complete the ship; and her engineer, overworked and worn out with worry, broke down and did not see her begin her first voyage on the 7th of September 1859. On the 5th he was brought home from the ship suffering from a paralytic stroke, and on the 15th he died at his house in Westminster.

In addition to the great works already described, Brunel was employed in the construction of many docks and piers, as at Monkwearmouth, Bristol, Plymouth, Briton Ferry, Brentford and Milford Haven. He was a zealous promoter of the Great Exhibition of 1851, and was a member of the committee on the section of machinery and of the building committee. He paid much attention to the improvement of large guns, and designed a floating gun-carriage for the attack on Kronstadt in the Russian War (1854); he also designed and superintended the construction of the hospital buildings at Erenkeni on the Dardanelles (1855). He was elected a fellow of the Royal Society in 1830, and in 1858 declined the presidency of the Institution of Civil Engineers through ill-health. He received the degree of D.C.L. from Oxford in 1857. In his work he was singularly free from professional jealousy, and was always ready to commend and help others, though, himself a man of remarkable industry and energy, he demanded a high standard of faithful service from his subordinates.

See The Life of I.K. Brunel, C.E. (1870), by his son, Isambard Brunel.