The year 1933 in science and technology involved some significant events, listed below.

• October 13 – The British Interplanetary Society is founded.
• Walter Baade and Fritz Zwicky invent the concept of the neutron star, a new type of celestial object, suggesting that supernovae might be created by the collapse of a normal star to form a neutron star.
• Sir Arthur Eddington publishes The Expanding Universe: Astronomy's 'Great Debate', 1900–1931 in Cambridge.
• Comedian Will Hay observes the periodic Great White Spot on Saturn from his private observatory in London.^[1]
• Fritz Zwicky postulates the existence of dark matter.^[2]

• Gilbert N. Lewis isolates the first sample of pure heavy water by electrolysis.^[3]
• Morris S. Kharasch and Frank R. Mayo propose that free radicals are responsible for anti-Markovnikov addition of hydrogen bromide to allyl bromide.^[4][5]

• March 10 – Long Beach earthquake in Southern California: First recording of earthquake strong ground motions by an accelerograph network, installed in 1932 by the United States Coast and Geodetic Survey.

• Andrey Kolmogorov publishes Foundations of the Theory of Probability, laying the modern axiomatic foundations of probability theory.^[6]
• David Champernowne, while still a Cambridge undergraduate, publishes his work on the Champernowne constant in real numbers.^[7][8]
• Alfréd Haar introduces Haar measure.^[9]
• Jerzy Neyman and Egon Pearson publish the Neyman–Pearson lemma.^[10]
• Stanley Skewes discovers Skewes' number.^[11]

• September 12 – Leó Szilárd, waiting for a red light on Southampton Row in Bloomsbury (London), conceives the idea of the nuclear chain reaction.

• April 3 – First attempted human kidney transplant, by Dr Yuri Voronoy in the Soviet city of Kherson; the recipient dies 2 days later due to incompatibility of blood type with the (cadaveric) donor.^{[12][13][14][15]}
• July 8 – English researchers Wilson Smith, Christopher Andrewes and Patrick Laidlaw report isolating a human influenza A virus and its transferability to ferrets.^[16]
• July 14 – Law for the Prevention of Hereditarily Diseased Offspring enacted in Nazi Germany^[17] allowing compulsory sterilization of citizens suffering from a list of alleged genetic disorders.
• Manfred Sakel begins to practice insulin shock therapy on psychiatric patients in Vienna.^[18]

• March 7 – The hydraulic torque converter is patented by Alf Lysholm.^[19]
• June – A research group at RCA headed by Vladimir K. Zworykin publicly launches the iconoscope, the first practical cathode ray tube television camera.^{[20][21][22][23]}
• June 26 – American Totalisator unveils its first tote board, the electronic pari-mutuel betting machine, at the Arlington Park race track near Chicago.

• Museum of Science and Industry (Chicago) first opens to the public, as part of the Century of Progress Exposition.
• The Institute for Advanced Study opens at Princeton, New Jersey, attracting Albert Einstein, John von Neumann and Kurt Gödel.
• Sheffield Trades Historical Society (later South Yorkshire Industrial History Society) established in England.

• Nobel Prizes
  • Physics – Erwin Schrödinger and Paul Dirac
  • Chemistry – not awarded
  • Physiology or Medicine – Thomas Hunt Morgan

• January 6 – Oleg Makarov (died 2003), Soviet cosmonaut.
• January 18 – David Bellamy (died 2019), English botanist.
• March 9 – Sir David Weatherall (died 2018), English molecular geneticist.
• March 10 – Patricia Bergquist (died 2009), New Zealand scientist specializing in anatomy and taxonomy.
• March 23 – Philip Zimbardo, American social psychologist.
• April 1 – Claude Cohen-Tannoudji, French physicist and Nobel laureate
• April 14 – Yuri Oganessian, Russian nuclear physicist.
• April 26 – Arno Allan Penzias (died 2024), German-born American physicist and radio astronomer.
• May 22 – Chen Jingrun (died 1996), Chinese mathematician.
• July 9 – Oliver Sacks (died 2015), English-born neurologist.
• July 12 – Max Birnstiel (died 2014), Swiss molecular biologist.
• August 10 – Ed Posner (died 1993), American mathematician.
• August 15
  • Stanley Milgram (died 1984), American social psychologist.
  • Michael Rutter (died 2021) English child psychiatrist.
• September 6 – Juliet Clutton-Brock (died 2015), English zooarchaeologist.
• September 10 – Yevgeny Khrunov (died 2000), Soviet cosmonaut.
• September 26 – Charles C. Conley (died 1984), American mathematician specializing in dynamical systems.
• October 2 – Sir John Gurdon, English developmental biologist, recipient of the Nobel Prize in Physiology or Medicine.
• October 9 – Sir Peter Mansfield (died 2017), English physicist, recipient of the Nobel Prize in Physiology or Medicine.
• November 1 – Dijen K. Ray-Chaudhuri, Bengali-born mathematician.
• November 4 – Sir Charles K. Kao (died 2018), Chinese electrical engineer and physicist, recipient of the Nobel Prize in Physics.
• December 22 – Thomas Stockham (died 2004), American electrical engineer and inventor
• December 23 – Akihito, ichthyologist and Emperor of Japan.

• January 14 – Sir Robert Jones, 1st Baronet (born 1857), Welsh orthopaedic surgeon.
• May 22 – Sándor Ferenczi (born 1873), Hungarian psychoanalyst.
• June 14 – Ernest William Moir (born 1862), British civil engineer.
• September 25 – Paul Ehrenfest (born 1880), Austrian physicist and mathematician.
• October 29
  • Albert Calmette (born 1863), French physician, bacteriologist and immunologist.
  • Paul Painlevé (born 1863), mathematician and statesman, 62nd Prime Minister of France.
• November 3 – Pierre Paul Émile Roux (born 1853), French physician, bacteriologist and immunologist.
• December 8 – John Joly (born 1857), Irish physicist.