The year 1625 in science and technology involved some significant events.

• First description of hydrogen by Johann Baptista van Helmont. First to use the word "gas".
• Johann Rudolf Glauber discovers sodium sulfate (sal mirabilis or "Glauber's salt", used as a laxative) in Austrian spring water.^[1]

• June 8 – Giovanni Cassini, Italian astronomer (died 1712)
• March 25 – John Collins, English mathematician (died 1683)
• August 13 – Rasmus Bartholin, Danish scientist (died 1698)
• December 16 – Erhard Weigel, German mathematician and scientific populariser (died 1699)
• December 20 – David Gregory, Scottish physician and inventor (died 1720)
• Samuel Morland, English inventor (died 1695)

• March 7 – Johann Bayer, German uranographer (born 1572)
• April 7 – Adriaan van den Spiegel, Flemish-born anatomist and botanist (born 1578)
• May 6 – George Bruce of Carnock, Scottish coal mining engineer (born c.1550)
• Ferrante Imperato, Neapolitan natural historian (born 1550)
• Willem Schouten, Dutch navigator, died at sea (born c. 1567)