1895 in science
- April 26 – The New York Zoological Society, the modern-day Wildlife Conservation Society, is chartered.
- David Bruce discovers the Trypanosoma parasite carried by the tsetse fly which causes the fatal cattle disease nagana.
- March 26 – Scottish chemist William Ramsay isolates helium on Earth by treating the mineral cleveite. These samples are identified as helium by Norman Lockyer and William Crookes. It is independently isolated from cleveite in the same year by Per Teodor Cleve and Abraham Langlet in Uppsala, Sweden, who determine its atomic weight.
- Emil Fischer and Arthur Speier first describe Fischer–Speier esterification.
- Carl von Linde filed for patent of the Linde cycle.
- December 11 – Svante Arrhenius delivers quantified data about the sensitivity of global climate to atmospheric carbon dioxide (the "Greenhouse effect") as he presents his paper "On the Influence of Carbonic Acid in the Air Upon The Temperature of the Ground" to the Royal Swedish Academy of Sciences.
- Eugen Warming publishes Plantesamfund (translated as Oecology of Plants, 1909) and founds the scientific discipline ecology.
- The first international meeting for the protection of birds is held in Paris.
- Diederik Korteweg and Gustav de Vries derive the Korteweg–de Vries equation, a description of the development of long solitary water waves in a canal of rectangular cross section.
- Georg Cantor publishes the first part of a paper on set theory containing the arithmetic of infinite cardinal numbers and the continuum hypothesis.
- Henri Poincaré publishes his paper "Analysis Situs", providing the first systematic treatment of topology.
- May 7 – Alexander Stepanovich Popov demonstrates a radio receiver (containing a coherer) refined as a lightning detector to the Russian Physico-Chemical Society, recognized as the first practical application of electromagnetic waves.
- November 8 – Wilhelm Röntgen discovers a type of electromagnetic radiation which he calls X-rays.
- February 13 – Auguste and Louis Lumière patent their cinematograph motion picture film camera/projector in France.
- May 6 – The Metropolitan West Side Elevated Railroad is opened in Chicago as the first electrically operated rapid transit system in the United States, including the first completed Scherzer rolling lift bridge.
- December 31 – Ogden Bolton Jr. is granted U.S. Patent 552,271 for an electric bicycle.
- The world's first portable handheld electric drill is developed by brothers Wilhelm and Carl Fein in Germany.
- Ernest A. Hummel invents the telediagraph.
- May – Publication of H. G. Wells' first "scientific romance", the novella The Time Machine (serial publication completed and first book editions).
- July 25 – Maria Skłodowska marries Pierre Curie in the town hall at Sceaux.
- January 11 – Laurens Hammond (died 1973), American inventor.
- January 15 – Artturi Ilmari Virtanen (died 1973), Finnish winner of the Nobel Prize in Chemistry.
- May 8 – Lionel Whitby (died 1956), English haematologist, clinical pathologist, pharmacologist and army officer.
- May 20 – R. J. Mitchell (died 1937), English aeronautical engineer.
- October 19 – Lewis Mumford (died 1990), American historian & philosopher of science.
- October 22 – Rolf Nevanlinna (died 1980), Finnish mathematician.
- October 23 – Hans Ferdinand Mayer (died 1980), German physicist.
- October 30
- December 2 – W. Conway Pierce (died 1974), American chemist.
- December 24 – Marguerite Williams (died 1991?), African-American geologist.
- Asatour Sarafian, later Oscar H. Banker (died 1979), Armenian American inventor.
- January 26 – Arthur Cayley (born 1821), English mathematician.
- April 11 – Lothar Meyer (born 1830), German chemist.
- May 5 – Karl Vogt (born 1817), German scientist who published notable works in zoology, geology and physiology.
- June 29 – Sir Thomas Henry Huxley (born 1825), English biologist.
- August 10 – Felix Hoppe-Seyler (born 1825), German physiologist.
- August 26 – Friedrich Miescher (born 1844), Swiss biologist.
- September 24 – Hermann Hellriegel (born 1831), German agricultural chemist who discovered the mechanism by which leguminous plants assimilate the free nitrogen of the atmosphere.
- September 28 – Louis Pasteur (born 1822), French biologist.
- December 27 – Eivind Astrup (born 1871), Norwegian Arctic explorer.
- Bruce, D. (1895). Preliminary Report on Tsetse Fly Disease or Nagana in Zululand. Durban: Bennet & Davis.
- Duggan, A. J. (1977). "Bruce and the African Trypanosomes". The American Journal of Tropical Medicine and Hygiene. 26 (5 Pt 2 Suppl): 1080–3. PMID 20787.
- Hampel, Clifford A. (1968). The Encyclopedia of the Chemical Elements. New York: Van Nostrand Reinhold. pp. 256–268. ISBN 0-442-15598-0.
- Ramsay, William (1895). "On a Gas Showing the Spectrum of Helium, the Reputed Cause of D3, one of the lines in the Coronal Spectrum. Preliminary Note". Proceedings of the Royal Society of London. 58 (1): 65–67. doi:10.1098/rspl.1895.0006.
- Ramsay, William (1895). "Helium, a Gaseous Constituent of Certain Minerals. Part I". Proceedings of the Royal Society of London. 58 (1): 80–89. doi:10.1098/rspl.1895.0010.
- Ramsay, William (1895). "Helium, a Gaseous Constituent of Certain Minerals. Part II". Proceedings of the Royal Society of London. 59 (1): 325–330. doi:10.1098/rspl.1895.0097.
- Munday, Pat (1999). "W.F. Hillebrand (1853–1925), geochemist and U.S. Bureau of Standards administrator". In Garraty, John A.; Carnes, Mark C. American National Biography. 10–11. Oxford University Press. pp. 808–9; 227–8.
- Emsley, John (2001). Nature's Building Blocks. Oxford University Press. pp. 175–179. ISBN 0-19-850341-5.
- Langlet, N. A. (1895). "Das Atomgewicht des Heliums". Zeitschrift für anorganische Chemie (in German). 10 (1): 289–292. doi:10.1002/zaac.18950100130.
- Weaver, E. R. (1919). "Bibliography of Helium Literature". Industrial & Engineering Chemistry.
- Fischer, Emil; Speier, Arthur (1895). "Darstellung der Ester". Chemische Berichte. 28 (3): 3252–3258. doi:10.1002/cber.189502803176.
- "On the Influence of Carbonic Acid in the Air Upon The Temperature of the Ground". The London, Edinburgh, and Dublin Philosophical Magazine and Journal of Science. April 1896.
- "The Endangered Species Act – History Of Species Protection". Science Encyclopedia. Library Index. Retrieved 2012-11-18.
- Korteweg, D. J.; de Vries, G. (1895). "On the Change of Form of Long Waves Advancing in a Rectangular Canal, and on a New Type of Long Stationary Waves". The London, Edinburgh, and Dublin Philosophical Magazine and Journal of Science. 39 (240): 422–443. doi:10.1080/14786449508620739.
- Cantor, Georg (1895). "Beiträge zur Begründung der transfiniten Mengenlehre (1)". Mathematische Annalen. 46 (4): 481–512. doi:10.1007/bf02124929. Archived from the original on 2014-04-23.
- Poincaré, Henri (1895). "Analysis situs". Journal de l'École Polytechnique. (2). Paris. 1: 1–123.
- "Report 12 of the Council on Scientific Affairs (A-97)". American Medical Association. 1997. Archived from the original on 2009-06-14. Lay summary (PDF) – 1997 Annual Meeting of the American Medical Association: Reports of the Council on Scientific Affairs (1997).
- "Popov's Contribution to the Development of Wireless Communication, 1895". IEEE Global History Network. Milestones. IEEE. Retrieved 2013-02-23.
- Röntgen, W. (December 1895). "Eine neue Art von Strahlen". Sityzungs-Berichteder physikalisch-medicinisch Gesellschaft zu Würzburg (9).
- "New "L" Road Opens". Chicago Daily Tribune. 1895-05-07. p. 12.
- "Cermak Road Bridge District" (PDF). City of Chicago. 2003. p. 17. Archived from the original (PDF) on January 31, 2012. Retrieved 2012-02-09.
- "Electrical Bicycle". Google Patents. 1895. Retrieved 2012-05-25.
- Morchin, William C.; Oman, Henry (2006). Electric Bicycles. Hoboken: Wiley. p. 3. ISBN 978-0-471-67419-1.