1849 in science
- Arnold Adolph Berthold pioneers endocrinology with his observations on the operation of the testicles in roosters.
- Nikolai Annenkov begins publication of Flora Mosquensis Exsiccata, the first Russian Flora.
- Richard Owen publishes On the Nature of Limbs and begins publication of A History of British Fossil Reptiles.
- William Thompson begins publication (in London) of The Natural History of Ireland with the first volume on birds.
- January 23 – English-born Elizabeth Blackwell is awarded her M.D. by the Medical Institute of Geneva, New York, becoming the first woman to qualify as a doctor in the United States.
- British physician Dr. Thomas Addison first describes Addison’s disease in his On the Constitutional and Local Effects of Disease of the Suprarenal Capsules.
- London physician Dr. John Snow first publishes his theory that cholera is a contagious disease of the human gastrointestinal tract in his pamphlet On the Mode of Communication of Cholera.
- April 10 – Walter Hunt is granted a United States patent for the modern safety pin.
- May 22 – Abraham Lincoln's patent: Abraham Lincoln is granted a United States patent for a buoyancy mechanism to lift boats over river shoals, the only patent ever granted to a President of the United States.
- June 20 – First tube of Robert Stephenson's Britannia Bridge is floated into position on the Menai Strait for the Chester and Holyhead Railway's North Wales Coast Line with many leading British railway civil engineers present.
- Completion of Wheeling Suspension Bridge over the Ohio River at Wheeling, West Virginia, designed by Charles Ellet, with a world record main span (at this date) of 1,010 ft (310 m) tower to tower.
- Eugene Bourdon patents the Bourdon gauge for pressure measurement in France.
- David Brewster perfects the stereoscope.
- James B. Francis develops the radial flow Francis turbine.
- February 28 – Regina von Siebold (b. 1771), German obstetrician.
- March 7 – Luther Burbank (died 1926), American plant breeder.
- April 19 – John Uri Lloyd (died 1936), American pharmacist and science fiction author.
- April 25 – Felix Klein (died 1925), German mathematician.
- May 25 – Louise Hammarström (died 1917), Swedish chemist.
- May 26 – Ernst Remak (died 1911), German neurologist.
- July 12 – William Osler (died 1919), Canadian physician.
- July 27 – John Hopkinson (died 1898), English electrical engineer.
- September 14 – Ivan Pavlov (died 1936), Russian physiologist.
- October 26 – Ferdinand Georg Frobenius (died 1917), German mathematician.
- Berthold, A. A. (1849). "Transplantation der Hoden". Arch. Anat. Physiol. Wiss. Med. 16: 42–6.
- Petrunkevitch, Alexander (1920). "Russia's Contribution to Science". Transactions of the Connecticut Academy of Sciences. 23: 232.
- "History of Chirality". Stheno Corporation. 2006. Archived from the original on 2007-03-07. Retrieved 2007-03-12.
- Hempel, Sandra (2006). The Medical Detective: John Snow and the mystery of cholera. London: Granta Books. ISBN 9781862078420.
- "Walter Hunt... Dress-Pin: Specification of Letters Patent No. 6,281". United States Patent and Trademark Office. 1849-04-10. Retrieved 2011-12-05.
- "Walter Hunt". National Inventors Hall of Fame. 2002. Archived from the original on 2011-08-05. Retrieved 2011-12-05.
- "Letters Patent No. 6,469". Google Patents. Retrieved 2011-12-29.
- "Britannia Bridge". Engineering Timelines. Retrieved 2014-06-10.
- Bellis, Mary. "Bourdon Tube Pressure Gauge". Inventors. About.com. Retrieved 2014-01-19.