The year 1989 in science and technology involved many significant events, some listed below.

• August – Asteroid 4769 Castalia is the first asteroid directly imaged, by radar from Arecibo.
• August 25 – The Voyager 2 spacecraft makes its closest approach to Neptune, providing definitive proof of the planet's rings.
• September 5 – Pluto–Charon barycentre comes to perihelion.^[1]
• Asteroid 5128 Wakabayashi is discovered by Masahiro Koishikawa.
• 4292 Aoba is discovered.
• 4871 Riverside is discovered.
• 6089 Izumi is discovered.
• 6190 Rennes is discovered
• 8084 Dallas is discovered.

• Discovery of the cystic fibrosis trans-membrane conductance regulator gene.^[2]
• The New Zealand Department of Conservation begins to implement a Kākāpō Recovery Plan.^[3]

• March 12 – Tim Berners-Lee submits a memorandum, titled "Information Management: A Proposal", to the management at CERN for a system that would eventually become the World Wide Web.
• June 8 – GNU Bash is released.^[4]
• July 26 – A federal grand jury indicts Cornell University student Robert Tappan Morris, Jr. for releasing a computer virus, making him the first person to be prosecuted under the 1986 Computer Fraud and Abuse Act in the United States.

• The global concentration of carbon dioxide in Earth's atmosphere reaches 350 ppm (parts per million) by volume.

• January – Supplee's paradox is published.^[5]
• March 23 – Stanley Pons and Martin Fleischmann announce cold fusion at the University of Utah.

• The Oxford Database of Perinatal Trials begins publishing online.^[6]
• The hepatitis C virus (HCV) is first identified by Michael Houghton and his team.

• July 17 – The Northrop Grumman B-2 Spirit "Stealth Bomber" aircraft, developed for the United States Air Force, first flies.^[7]
• Isamu Akasaki produces the first Gallium nitride p-n junction blue/UV light-emitting diode.

• Nobel Prizes
  • Physics – Norman F. Ramsey, Hans G. Dehmelt, Wolfgang Paul
  • Chemistry – Sidney Altman, Thomas R. Cech
  • Medicine – J. Michael Bishop, Harold E. Varmus
• Turing Award – William (Velvel) Kahan

• May 9 – Katie Bouman, American computer imaging scientist

• February 27 – Konrad Lorenz (born 1903), Austrian zoologist.
• March 18 – Sir Harold Jeffreys (born 1891), English mathematician.
• April 24 – Horace Hodes (born 1907), American medical researcher.
• August 10 – Isabella Forshall (born 1900), English pediatric surgeon.
• August 12 – William Shockley (born 1910), American physicist.
• August 20 – George Adamson (born 1906), British wildlife conservationist.
• August 29 – Sir Peter Scott (born 1909), English wildlife conservationist.
• October 11 – M. King Hubbert (born 1903), American geophysicist.
• October 28 – Louise Hay (born 1935), French-born American mathematician; breast cancer.
• December 14 – Andrei Sakharov (born 1921), Soviet Russian nuclear physicist and political dissident.