Joseph Mallord William Turner (1775-1851) was born on St George's Day (23 April) in 1775, the eldest son of a barber in Covent Garden, London. His mother suffered from mental illness, and died in Bethlem Hospital in 1804. Encouraged by her relatives, he began to pursue the life of an artist, and entered the Royal Academy Schools in December 1789.

His first exhibit at the Royal Academy in 1790 was a watercolour. He soon made a name with topographical watercolours, pursuing a similar career to Thomas Girtin. He visited Wales in 1792 and 1795, and the North of England in 1797, including the Lake District. Much work was undertaken to be engraved, such as scenes for the Copper-Plate Magazine (1794-1798) and the Oxford Almanack (1798-1804). Commissions followed from important patrons including Edward Lascelles, 1st Earl of Harewood, Sir Richard Colt Hoare and William Beckford.

His first oil painting was shown at the Royal Academy in 1796, of which he was elected an Associate ( A.R.A.) in 1799, and a full Member ( R.A.) in 1802. Like many artists, he took advantage of the Peace of Amiens in that year to travel to France and Switzerland, the only time this was possible during the Napoleonic Wars. This tour gave rise to some of his most important early works, in oil and watercolour, such as the Lake of Geneva, with Mont Blanc (c.1805), which Ruskin later owned.

Turner was elected Professor of Painting at the Royal Academy in 1811, and his growing reputation was enhanced by the Liber Studiorum project of mezzotint engravings of landscape and historical subjects, of which the first volume had been published in 1807. From 1804, he had opened a gallery for the exhibition of his own work, at his house in Harley Street (later extended into Queen Anne Street). Here, as well as at the Royal Academy, could be seen the great paintings that emerged in the next decade, including Thomson's Æolian Harp (1809), Snow Storm: Hannibal and his army crossing the Alps (1812), Dido and Æneas (1814) and The Decline of the Carthaginian Empire (1817). These last were painted to emulate the work of Claude.

Over sixty watercolours were displayed at the London house of his patron Walter Fawkes in 1819, and in the summer of that year Turner embarked on his first visit to Italy, a six-month tour encompassing Florence, Rome, Venice and Naples. He returned for a similar tour in 1828. The intervening years saw extensive travel in France, Scotland, Holland and the Rhineland, as well as throughout England, producing a huge number of drawings and sketches, as the basis for both oils and watercolours. Again, many were made for engraving, such as the series of Picturesque Views in England and Wales (1827 onwards) and the Rivers of Europe project (c.1825-34). Some of these watercolours were shown at the galleries of dealers and publishers such as Colnaghi and Moon, Boys and Graves.

Further travel in the 1830s included a visit to Delacroix's studio in Paris, probably in 1833, and in the summer of 1836 he toured France and Switzerland with one of his chief patrons, H.A.J. Munro of Novar. Venice became the source for many compositions, after visits in 1833 and 1840.

In the 1830s, Turner's oil paintings became more ambitious and more personal in style, the lingering classicism of Childe Harold's Pilgrimage (1832) and The Golden Bough (1834) being supplemented by dramatic and atmospheric paintings, among them The burning of the Houses of Lords and Commons (1835), Juliet and her nurse (1836), and Avalanche and Inundation (1837). These works prompted the critical attack on Turner which led to Ruskin 's defence of the artist and the writing of Modern Painters.

In his later years, Turner became increasingly reclusive, resigning the Professorship of Perspective in 1837 and concentrating on his work. He met Ruskin for the first time in June 1840, although John and his father John James Ruskin had been collectors of Turner's watercolours for several years (see Ruskin as a collector of Turner). Turner was aware of Ruskin's championship of his work, but rarely acknowledged it, while remaining on friendly terms (see Ruskin and Turner). The Ruskins were among the select group of collectors offered the choice from the magnificent series of Swiss watercolours emanating from Turner's tours between 1841and 1845, the highpoint of his work in the medium, but little known to the public, as they were not exhibited.

While some of his later paintings were appreciated, such as The Téméraire (1839) and Peace - burial at sea (1842), others mostly provoked criticism and general bafflement, including some of his most famous: Snow storm - steam-boat off a harbour's mouth (1842), Rain, Steam and Speed (1844), The Angel standing in the sun (1846). He was, however, the senior Royal Academician, and in 1845 carried out duties during the President's illness. His own declining health meant that his last works were exhibited in 1850, and he died on 19 December 1851. By his own wish, he was buried in the crypt of St. Paul's Cathedral, the funeral attracting a large gathering of his admirers.