1801 in science
- January 1 – Italian astronomer Giuseppe Piazzi makes the first discovery of an asteroid, Ceres, which is briefly considered to be the eighth planet.
- July 11 – French astronomer Jean-Louis Pons makes the first of his 37 comet discoveries.
- Jérôme Lalande and his staff at the Paris Observatory publish the astrometric star catalogue Histoire Céleste Française.
- Jean-Baptiste Lamarck publishes Système des animaux sans vertèbres in Paris, a major work on the classification of the group of animals he is the first to describe as invertebrates. He is also first to separate the classes of arachnids and crustaceans from insects.
- André Michaux publishes Histoire des chênes de l'Amerique septentrionale ("History of the oaks of North America").
- November 26 – Charles Hatchett announces to the Royal Society his discovery of the chemical element niobium, which he calls "columbium", in the ore columbite (it is renamed in 1950).
- Vanadium, a transition metal, is discovered by Andrés Manuel del Río in Mexico.
- René Just Haüy publishes his Traité de minéralogie.
- Carl Friedrich Gauss's textbook on number theory, Disquisitiones Arithmeticae, is published in Leipzig.
- William Playfair produces the first pie chart and circle graph, to show part-whole relations.
- Xavier Bichat publishes his Anatomie générale.
- Philippe Pinel publishes Traité médico-philosophique sur l'aliénation mentale; ou la manie, presenting his enlightened humane psychological approach to the management of psychiatric hospitals. Translated into English by D. D. Davis as Treatise on Insanity in 1806, it is influential on both sides of the Atlantic during the 19th century.
- Antonio Scarpa publishes Saggio di osservazioni e d'esperienze sulle principali malattie degli occhi, earning him the title "father of Italian ophthalmology".
- Samuel Thomas von Sömmerring publishes Abbildungen des menschlichen Auges, including the first description of the macula in the retina of the human eye.
- Dalton's law: John Dalton observes that the total pressure exerted by a gaseous mixture is equal to the sum of the partial pressures of each individual component in a gas mixture.
- Ultraviolet radiation is discovered by Johann Wilhelm Ritter.
- In optics, interference between light beams is discovered by Thomas Young, showing the wave nature of light.
- July – Eli Whitney demonstrates before the United States Congress the advantages of the system of interchangeable parts in the manufacture of firearms.
- October 20 – First patent for the Fourdrinier continuous paper machine in England.
- Joseph-Marie Jacquard develops the Jacquard Loom, in which holes strategically punched in a pasteboard card direct the movement of needles, thread, and fabric.
- The first iron (chain) suspension bridge is built by James Finley at Jacob’s Creek in Westmoreland County, Pennsylvania.
- The xaenorphica, a bow-stringed instrument with a keyboard, is invented by C. L. Röllig of Vienna (the strings are set in vibration by violin bows).
- January 22 – Friedrich Gerke, German pioneer of telegraphy (died 1888)
- April 19 – Gustav Fechner, German psychologist (died 1887)
- May 17 – Lovisa Åhrberg, Swedish surgeon (died 1881)
- June 16 – Julius Plücker, German mathematician and physicist (died 1868)
- July 14 – Johannes Peter Müller, German physiologist (died 1858)
- July 31 – George Biddell Airy, English astronomer (died 1892)
- Foderà Serio, G.; Manara, A.; Sicoli, P. (2002). "Giuseppe Piazzi and the Discovery of Ceres". In Bottke, W. F., Jr.; Cellino, A.; Paolicchi, P.; Binzel, R. P. Asteroids III (PDF). Tucson: University of Arizona Press. pp. 17–24. Archived from the original (PDF) on 27 September 2007. Retrieved 8 October 2007.
- Everett, Jason M., ed. (2006). "1801". The People's Chronology. Thomson Gale.
- Friendly, Michael (2008), Milestones in the history of thematic cartography, statistical graphics, and data visualization (PDF), pp. 13–14, retrieved 2008-07-07
- Foucault, Michel (1961). Folie et déraison: histoire de la folie à l'âge classique.
- Sebastian, Anton (1999). A Dictionary of the History of Medicine. Informa Health Care. ISBN 978-1-85070-021-0.
- Hermann, Armin (1987). "Unity and metamorphosis of forces (1800–1850): Schelling, Oersted and Faraday". In Doncel, M. G.; Hermann, A.; Michel, L.; Pais, A. Symmetries in Physics (1600–1980). Universitat Autònoma de Barcelona. pp. 51–62.
- Frercksa, Jan; Weberb, Heiko; Wiesenfeldt, Gerhard (2009). "Reception and discovery: the nature of Johann Wilhelm Ritter's invisible rays". Studies in History and Philosophy of Science Part A. 40 (2): 143–156.
- Van Dusen, Albert E. (2003). "Eli Whitney". Laptop Encyclopedia of Connecticut History. CTHeritage.org. Retrieved 2011-12-24.
- "Iron Wire of the Wheeling Suspension Bridge". Smithsonian Museum Conservation Institute. Archived from the original on 30 April 2011. Retrieved 18 April 2011.