Jan Ingenhousz (December 8, 1730 - September 7, 1799) was a Dutch-born British physiologist and botanist. He is best known for his discovery of the process of photosynthesis.

He discovered that in the presence of light plants give off bubbles from their green parts, while in the shade the bubbles eventually stop. This he discovered was oxygen. He also discovered that in the dark plants give off carbon dioxide. He realised as well that the amount of oxygen given off in the light is more than the amount of carbon dioxide given off in the dark. This proved that the solid matter of plants comes from the air and not the soil.