| 1730–1807 | UK [newspapers] | The Daily Advertiser is launched in London, England. With its dependence on advertisements, this may be regarded as the first modern newspaper. |
| 1784 | France [painting] | The French neoclassical artist Jacques-Louis David paints one of his best-known works, The Oath of the Horatii. |
| 1784 | England [painting] | The English artist Joshua Reynolds paints his portrait of Sarah Siddons (a well-known actor) as The Tragic Muse. |
| 1784 | France [plays] | The play Le Mariage de Figaro/The Marriage of Figaro by the French writer Pierre-Augustin Caron de Beaumarchais is performed, in Paris, France. An unparalleled success, it is used in 1786 as the basis of Mozart's opera. |
| 1784 | England [technology] | English iron manufacturer Henry Cort discovers the ‘puddling process’ of converting pig iron into wrought iron. It revolutionizes the manufacture of iron, production of which quadruples over the next 20 years. |
| 1784 | England [technology] | English engineer and inventor Joseph Bramah invents an improved ‘pick-proof’ lock. |
| 1784 | USA [technology] | US scientist and statesman Benjamin Franklin invents glasses with bifocal lenses. |
| 1784 | USA [technology] | US engineer Oliver Evans invents an automated process for grinding grain and sifting flour; it marks the beginning of automation in America. |
| 1784 | Swiss Confederation [technology] | Swiss inventor Aimé Argand invents an oil-burner consisting of a cylindrical wick, two concentric metal tubes to provide air, and a glass chimney to increase the draught. It gives a light ten times brighter than previous lamps and the principle is later used in gas-burners. |
| 1784 | Germany [canals] | The German River Eider is linked to the Baltic by canal; it becomes the prototype canal for international ship traffic. |
| 1784 | England [chemistry] | English chemist and physicist Henry Cavendish discovers that water is a compound of hydrogen and oxygen. |
| 1784 | France [architecture] | The French architect Etienne-Louis Boullé designs his Monument for Isaac Newton, in the form of a planetarium. It is never built. |
| 1784 | America [legislation] | The American states of Connecticut and Rhode Island abolish slavery. |
| 6 January 1784 | Ottoman Empire, Russia, Crimea-Ottoman [treaties] | By the terms of the Treaty of Constantinople, the Ottoman Empire acquiesces in Russia's annexation of the Crimea and the Caucasian region of Kuban. |
| 28 February 1784 | UK, America [Christianity] | The English evangelist John Wesley signs a deed of declaration as the charter of Wesleyan Methodism and ordains two ‘Presbyters’ for the American Mission. |
| 11 March 1784 | India [treaties] | Britain signs a peace treaty with Tippu Sultan of Mysore, India, ending the Second Mysore War. |
| 4 July 1784 | Habsburg Monarchy [legislation] | The Habsburg monarch and Holy Roman Emperor Joseph II of Austria repeals the constitution of Hungary as part of his campaign to create a unified Habsburg empire and to break the power of the local Hungarian nobility. |
| 30 July 1784 | France [births and deaths] | Denis Diderot, French philosopher of the Enlightenment, editor of the Encyclopédie/Encyclopedia, dies in Paris, France (71). |
| 13 December 1784 | England [births and deaths] | Samuel Johnson, English essayist, critic, and lexicographer, author of the Dictionary of the English Language, dies in London, England (74). |
