The year 1862 in science and technology involved some significant events, listed below.

• January 31 – Alvan Graham Clark makes the first observation of Sirius B, a white dwarf star, through an eighteen-inch telescope at Northwestern University in Illinois.

• May 15 – Charles Darwin publishes On the various contrivances by which British and foreign Orchids are fertilised by insects, and on the good effects of intercrossing.
• Henry Walter Bates publishes "Contributions to an insect fauna of the Amazon valley. Lepidoptera: Heliconidae"^[1] describing Batesian mimicry.
• George Bentham and Joseph Dalton Hooker begin publication of Genera plantarum based on the collections of the Royal Botanic Gardens, Kew, England.^[2]
• John Gwyn Jeffreys begins publication of British Conchology, or an account of the Mollusca which now inhabit the British Isles and the surrounding seas.

• Chemist and composer Alexander Borodin describes the first nucleophilic displacement of chlorine by fluorine in benzoyl chloride.^[3]
• Mineralogist Alexandre-Emile Béguyer de Chancourtois makes the first proposal to arrange the chemical elements in order of atomic weights, although this is largely ignored by chemists.^[4]
• Alexander Parkes exhibits Parkesine, one of the earliest synthetic polymers, at the International Exhibition in London. This discovery forms the foundation of the modern plastics industry.^[5]

• Friedrich Albert Fallou publishes "Pedologie oder allgemeine und besondere Bodenkunde" (Pedology or general and special soil science), founding soil science.^[6]

• Maurice Raynaud describes the vasospastic syndrome named after him in his doctoral dissertation.^[7]
• Hermann Snellen publishes the Snellen chart for testing visual acuity.

• July 8 – Theodore Timby is granted a United States patent for discharging guns in a revolving turret, using electricity.
• November 4 – Richard Jordan Gatling is granted a United States patent for the Gatling gun.
• Brown & Sharpe produce the first Universal Milling machine.^[8]
• David Kirkaldy publishes Results of an Experimental Inquiry into the Comparative Tensile Strength and other properties of various kinds of Wrought-Iron and Steel in Glasgow describing his pioneering work in tensile testing.

• Copley Medal: Thomas Graham^[9]
• Wollaston Medal for geology: Robert Godwin-Austen

• January 23 – David Hilbert (died 1943), German mathematician
• February 14 – Agnes Pockels (died 1935), German chemist (in Venice)
• March 14 – Vilhelm Bjerknes (died 1951), Norwegian physicist and meteorologist
• May 27 – John Edward Campbell (died 1924), Irish-born mathematician
• June 7 – Philipp Lenard (died 1947), German physicist
• June 9 – Ernest William Moir (died 1933), British civil engineer
• July 2 – William Henry Bragg (died 1942), English winner of the 1915 Nobel Prize in Physics
• August 2 – Paul Bujor (died 1952), Romanian animal morphologist, politician and short story writer
• October 12 – Theodor Boveri (died 1915), German geneticist
• October 19 – Auguste Lumière (died 1954), French inventor, film pioneer
• November 23 - Ernest Guglielminetti (died 1943), Swiss physician^[10]
• William Hoskins (died 1934), American inventor

• January 10 – Samuel Colt (born 1814), American inventor
• February 3 – Jean-Baptiste Biot (born 1774), French physicist
• February 7 – Prosper Ménière (born 1799), French physician who first described the symptoms of Ménière's disease
• February 11 – Luther V. Bell (born 1806), American psychiatric physician
• March 1 – Peter Barlow (born 1776), English mathematician
• April 3 – Sir James Clark Ross (born 1800), English explorer of the Polar regions
• May 6 – Olry Terquem (born 1782), French Jewish geometer
• October 8 – James Walker (born 1781), Scottish-born civil engineer
• October 21 – Sir Benjamin Collins Brodie, 1st Baronet (born 1783), English physiologist
• December 18 – Lucas Barrett (born 1837), English naturalist (drowned)
• December 20 – Robert Knox (born 1791), Scottish anatomist
• December 21 – Karl Kreil (born 1798), Austrian astronomer