The year 1865 in science and technology included many events, some of which are listed here.

Awards

• Copley Medal: Michel Chasles
• Wollaston Medal in Geology: Thomas Davidson

Births

Deaths

• August 26 - Johann Franz Encke (b. 1791), astronomer.
• September 2 - William Rowan Hamilton (b. 1805), mathematician, physicist, and astronomer.