Jonas, distinguished for his benevolent designs and useful writings, was born at Portsmouth, in Hampshire, on the 12th of August 1712. His father, Thomas Hanway, an officer in the naval service, and for some years storekeeper to the dockyard at that place, was deprived of his life by an accident, and left his widow with four children, Jonas, William, Thomas, and Elizabeth, all of very tender age. Mrs Hanway having repaired to London after the death of her husband, put Jonas to school, where he learned writing and accounts, and made some proficiency in Latin. At the age of seventeen he was sent to Lisbon, where he arrived in June 1729, and was bound apprentice to a merchant in that city. On the expiration of his apprenticeship, he entered into business at Lisbon as a merchant or factor; but he did not remain there long before he returned to London.

He soon afterwards connected himself as a partner in Mr Dingley's house in St Petersburg, where he arrived on the 10th of June 1743. The trade of the English nation by the Caspian Sea to Persia had at this period been intrusted to the care of Mr Elton, who, not content with the pursuit of commercial affairs, had injudiciously engaged in the service of Nadir Shah, to build ships on the Caspian after the European manner. This had alarmed the merchants engaged in the Russian trade, and a resolution was formed that one of their body should make a journey into Persia. On this occasion Mr Hanway offered his service, and was accepted. He set out on the 10th of September, and, after experiencing a great variety of hazards in that kingdom during the course of twelve months, returned to St Petersburg on the first of January 1745, without having been able to establish the intended trade by the Caspian, partly through the jealousy of the Russian court on account of Elton's connections with the Persians, and partly from the troubles and revolutions by which the latter kingdom was distracted.

He now settled at St Petersburg, where he remained five years. During this time he interested himself greatly in the concerns of the merchants who had engaged in the Caspian trade; but the independence he had acquired having excited a desire to revisit his native country, he left St Petersburg on the 9th of July 1750. In 1753 he published an Historical Account of the British Trade by the Caspian Sea, with a Journal of Travels from London through Russia into Persia, and back again through Russia, Germany, and Holland; a work which was received with great attention by the public. In 1754, we find Mr Hanway commending a plan offered for the advantage of Westminster, and suggesting hints for the further improvement of it, in a letter to Mr John Spranger on his excellent proposal for paving, cleansing, and lighting the streets of Westminster, Svo. A few years afterwards, when a scheme of the same kind was carried into effect, many of Mr Hanway's ideas, thrown out in this pamphlet, were adopted. In 1756, he printed a Journal of Eight Days' Journey from Portsmouth to Kingston-upon-Thames, with an Essay upon Tea, which was afterwards reprinted in two volumes Svo, 1757.

At this juncture, Great Britain being on the eve of a war with France, Hanway published Thoughts on the Duty of a good Citizen with regard to War and Invasion, in a Letter from a Citizen to his Friend, Svo. About the same time, several gentlemen formed a plan which was matured and perfected by the assiduity of Hanway, for providing the navy with sailors, by furnishing poor children with necessaries to equip them for the service of the country. The success and propriety of this scheme soon became apparent. Mr Hanway wrote and published three pamphlets on the occasion; and the treasurer of the society, accompanied by Mr Hanway, having waited on the king, the society received £1000 from his majesty, £400 from the prince of Wales, and £200 from the princess dowager. This excellent institution was through life the favourite object of Mr Hanway's care, and it continued to flourish under his auspices, greatly to the advantage of the community. In 1758 he became an advocate for another charitable institution, which derived considerable emolument from his patronage. This was the Magdalen Charity, to assist which he published a Letter to Robert Dingley, Esq. containing a Proposal for the Relief and Employment of friendless Girls and repenting Prostitutes, &c. He also printed other small performances on the same subject.

In 1759, Mr Hanway wrote Reasons for an Augmentation of at least Twelve Thousand Mariners to be employed in the Merchants' Service and Coasting Trade, &c. The next year he published several productions, viz. 1. A candid historical Account of the Hospital for the reception of exposed and deserted young Children, Svo; 2. An Account of the Society for the Encouragement of the British Troops in Germany and North America, Svo; 3. Eight Letters to —— Duke of ——, on the Custom of Vails giving in England, Svo. In 1761, he produced Reflections, Essays, and Meditations on Life and Religion, with a collection of Proverbs, and eighteen Letters written occasionally on several subjects, in 2 vols, Svo.

In July 1762, he was appointed one of the commissioners for victualling the navy; a post which he held above twenty-one years. His attention having been particularly directed towards alleviating the miseries of young chimney-sweepers, he published, in 1773, the State of the Chimney-sweepers' Young Apprentices, showing the Happiness, wretched condition of these distressed boys, the ill conduct of such masters as do not observe the obligation of Indentures, and the necessity of a strict inquiry in order to support the civil and religious rights of these apprentices, 12mo. In the succeeding year, 1774, he enlarged a former publication, entitled Advice from a Farmer to his Daughter, and republished it under the title of Virtue in Humble Life, containing Reflections on the Reciprocal Duties of the Wealthy and Indigent, the Master and the Servant, 2 vols. 8vo. This edition being sold, in a few months he reprinted it in two-quarto volumes, with a dedication to Mrs Montagu.

In 1783, finding his health decline, he determined to resign his office at the victualling board, which he did on the 2d of October that year; and immediately received a grant of his whole salary by way of pension during his life. In the summer of 1786 Mr Hanway's health declined visibly. He had long felt the approach of a disorder in the bladder, which, increasing by degrees, caused a strangury, and at length, on the 5th of September 1786, put a period to a life spent almost entirely in the service of his fellow-creatures. On the 13th he was interred in the family-vault at Hanwell, being attended to the grave by a numerous retinue of friends; and after his death the public regard for his virtues was displayed by a subscription of several hundred pounds for erecting a monument to perpetuate his memory.