The year 1984 in science and technology involved some significant events.

• February 7 – Astronauts Bruce McCandless II and Robert L. Stewart make the first untethered space walk.
• The National Radio Astronomy Observatory in the United States converts the 36-foot radio telescope on Kitt Peak (originally built in 1967) to the ARO 12m Radio Telescope.

• First known case of Bovine spongiform encephalopathy, in England.^[1]
• The enzyme telomerase is discovered by Carol W. Greider and Elizabeth Blackburn in the ciliate Tetrahymena.^[2]
• Danish physiologist Steen Willadsen first successfully uses cells from early embryos to clone a mammal (sheep) by nuclear transfer at the British Agricultural Research Council's Institute of Animal Physiology, Cambridge.^[3][4]

• Peter Kramer^[5] and Dan Shechtman^[6] publish their discoveries of what will soon afterwards be named quasicrystals.^[7]
• Hiroshi Kobayashi and colleagues announce synthesis of tetrakis(3,5-bis(trifluoromethyl)phenyl)borate ("BARF").^[8]

• January 24 – Apple Computer places the Macintosh personal computer on sale in the United States. It will be the first successful PC to use a graphical user interface.
• The first edition of language documentation Common Lisp the Language (known as CLtL1) is published in the United States.

• Robert Gwyn Macfarlane publishes Alexander Fleming: The Man and the Myth.

• The fossil skeleton of the hominid "Turkana Boy" is discovered in Kenya.

• February 3 – Dr. John Buster and the research team at Harbor-UCLA Medical Center announce history's first embryo transfer from one woman to another resulting in a live birth.
• April 22 – Dr. Robert Gallo and Margaret Heckler of United States Public Health Service announce the discovery of HTLV-III as the virus that causes AIDS.
• May 10 – Barbara H. Bowman and Oliver Smithies show that variations in haptoglobins are due to genetic polymorphisms.^[9]

• May 5 – Itaipu Dam in South America begins to generate hydroelectricity.
• July 21 – In Jackson, Michigan, a factory robot crushes a worker against a safety bar in apparently the first robot-related death in the United States.

• Nobel Prizes
  • Physics – Carlo Rubbia, Simon van der Meer
  • Chemistry – Robert Bruce Merrifield
  • Medicine – Niels K. Jerne, Georges J. F. Köhler, César Milstein
• Turing Award – Niklaus Wirth

• May 14 – Mark Zuckerberg, American computer programmer and entrepreneur, co-founder of social media platform Facebook
• December 2 – Maryna Viazovska, Ukrainian-born mathematician^[10]

• January 8 – Eerik Kumari (b. 1912), Estonian ornithologist and academic
• February 21 – Anna Baetjer (b. 1899), American toxicologist.
• April 8 – Pyotr Kapitsa (b. 1894), Russian physicist, Nobel Prize laureate.
• April 15 – Grete Hermann (b. 1901), German mathematician and philosopher
• May 13 – Stanislaw Ulam (b. 1909), Polish American mathematician.
• May 24 – Sir Stanley Hooker (b. 1907), English aeronautical engineer.
• August 6 – Abraham Lilienfeld (b. 1920), American epidemiologist.
• August 11 – George Streisinger (b. 1927), Hungarian American molecular biologist, the first person to clone a vertebrate.
• October 20 – Paul Dirac (b. 1902), English-born physicist.
• November 20 – Charles C. Conley (b. 1933), American mathematician working on dynamical systems.
• December 20 – Stanley Milgram (b. 1933), American social psychologist.