Admiral William Henry Smyth KFM DCL FRS FSA FRAS FRGS (21 January 1788 – 8 September 1865) was an English Royal Navy officer, hydrographer, astronomer and numismatist.

He is noted for his involvement in the early history of a number of learned societies, for his hydrographic charts, for his astronomical work, and for a wide range of publications and translations.

[3] Their claims, which were reproduced in works like Burke's Peerage,[4] included alleged descent from the childless Captain John Smith, whose coat of arms they adopted, and a fictitious relationship with Lord Nelson.

[3] Genealogical research they had commissioned in England and the USA, suggesting that his father Joseph Smyth was in fact a forger, a perjurer and a bigamist, was suppressed.

[3] In 1802, aged 14, Smyth ran away from his poverty-stricken home to be a cabin boy aboard a merchant ship, which was subsequently commandeered by the Royal Navy; he entered as an ordinary seaman.

In the following March, as Cornwallis the vessel was bought by the Royal Navy to be a 50-gun ship under the command of Captain Charles James Johnston, with whom Smyth remained, seeing much active service in Indian, Chinese, Australian and Pacific waters.

He afterwards served in the 74-gun Milford on the coast of France and Spain, and was lent from her to command the Spanish gunboat Mors aut Gloria at the defence of Cadiz from September 1810 to April 1811.

[5] On 25 March 1813 (aged 25) he was promoted to lieutenant and appointed to the Sicilian flotilla, in which he combined service against the French from Naples with a good deal of unofficial hydrographic surveying and antiquarian research.

In Aid, Smyth carried on the hydrographic survey of the Italian, Sicilian, Greek, and African coasts, and constructed a very large number of charts, used by the Royal Navy among others until the mid-20th century.

His hydrographic operations in the Adriatic, in collaboration with the Austrian and Neapolitan authorities, resulted in the Carta di Cabottaggio del Mare Adriatico, published in 1822–24.

Smyth published some of his work in his Memoir description of the Resources, Inhabitants, and Hydrography of Sicily and its Islands (London, 1824),[8] which was followed in 1828 by a Sketch of Sardinia.

Many of these descriptions are especially valuable for the novice and user of small telescopes of a size similar to Smyth's.Having completed his observations, he moved to Cardiff in 1839 to supervise the construction of the Bute Dock which he had designed.

[32][5] As well as his home at St John's Lodge in Stone, he kept a house at 3 Cheyne Walk in Chelsea, London, where he stayed while attending the various learned societies and where he entertained his like-minded friends.

He died a few hours later, in the early morning of 9 September, at the age of 78, and was buried in the graveyard of St John the Baptist church at Stone, Buckinghamshire.