John Oswald (c. 1760/1730 – 14 September 1793) was a Scottish philosopher, writer, poet, social critic and revolutionary.
Little is known for certain regarding Oswald's early life. He was born between 1755 and 1760 in Edinburgh. His father is said to have been a coffee-house-keeper, or a goldsmith. He became a student goldsmith himself. It is said that Oswald learned Latin and Greek without a tutor, and later learned Arabic.
Oswald served in the British Army as a Lieutenant of the Royal Highland Regiment, the forty-second regiment of foot. He served as a recruiting officer in Scotland during the American Revolution, and then in 1780 to the Malabar Coast of India. Oswald's exposure to Hindu vegetarianism in India influenced his philosophy which he describes in The Cry of Nature or An Appeal to Mercy and Justice on Behalf of the Persecuted Animals, published in 1791. This is considered an important work of western vegetarianism.
Oswald could no longer continue as an army officer. He left the army and returned to Britain in 1783, and began a period as an author of poetry and social criticism, and editor of The British Mercury, a periodical publication. During this period, Oswald wrote a sharp polemic in favour of republicanism, Review of the Constitution of Great Britain, and an anti-religious leaflet Ranae Comicae Evangelizantes: or the Comic Frogs turned Methodist, in which he supported atheism.
With the outbreak of the French Revolution of 1789, Oswald travelled to Paris, and soon joined the Jacobin Club. In that body, he pressed for more energetic intervention by the Jacobins in British affairs, arguing that a revolution in England was essential for peace between the two nations. An address to a Manchester radical organization was sent by the Jacobins on Oswald's urgings. According to some reports, Oswald was sent to Ireland to offer French support for an Irish rebellion, but little appeared to come of this effort.