Giles Firmin Phillips was an English artist and author. He painted landscapes and river scenes, primarily of the river Thames. His paintings were exhibited, among other venues, at the Royal Academy from 1836 - 1858. He is the author of several books on painting and lithography.

Phillips was born in 1780, the youngest child of John and Dorothy Phillips (sometimes spelled Philips). Nothing is known about Giles’ childhood and adolescence. He was not taught at the Royal Academy Schools. However, he was apprenticed by his father to James Harrison (later Harrison & Co.,) of Paternoster Row, Printer, on 1 April 1794, which was registered with the Stationers Company on 30 March. Harrison published engravings, lithographs and magazines, and Giles must have learned to draw by copying and engraving plates. He published a book on Lithography or 'drawing on stone' in 1828.

The first record of his artistic inclination is his engraving of Lady Eliza Wrixon-Becher, a celebrated actress of the time, which was published by A. Beugo in 1815 when Giles was 35 years old. Another engraving, this time of Sarah Siddons, was published, also by A. Beugo, in 1825. During the latter years Giles was moving fairly frequently. There are records of his insurance policies, taken out with the Sun Fire Office in the early 1820s which show him living at 4, Craven Street, City Road in 1822 and 35, Tavistock Street, Covent Garden by 1825, and described as an engraver. By 1827 he was living at 16 Brownlow Street, off High Holborn, and he is described as a “Drawing Master” in the directories of the time. His son John was also living with the family at the time.

He was a founder member of the New Watercolour Society (founded 1831, and renamed "The Institute of Painters in Watercolours" in 1863.) He joined in 1832 soon after its foundation, and was on the committee of Management in 1833, for a year. He was also a professional subscriber in 1834, but according to the catalogues was neither a member nor exhibitor after 1835. He was described as an eccentric old watercolour painter, well known in his day.

Phillips married Lydia Arnold on 11 June 1800. They are the parents of author/illustrator John Phillips. Giles Phillips was also the great uncle of illustrator, author and playwright Watts Phillips.

According to his death certificate, Phillips died on 31 March 1867 in Islington. He was buried at the Holy Trinity Church, East Finchley.