Aerobiology (from Greek ἀήρ, aēr, "air"; βίος, bios, "life"; and -λογία, -logia) is a branch of biology that studies organic particles, such as bacteria, fungal spores, very small insects, pollen grains and viruses, which are passively transported by the air (Spieksma, 1991). Aerobiologists have traditionally been involved in the measurement and reporting of airborne pollen and fungal spores as a service to allergy sufferers (Larsson, 1993).

In 2002, algae and other small water-borne organisms were discovered to inhabit clouds. A large cloud has about as much water as a shallow lake of the same geographic size.

An important medical application of aerobiology is the study of the transmission of airborne diseases. It is known that many bacteria and viruses can be transmitted by spread through the air, possibly within droplets.

Aerobiology is a rapidly developing science, which also involves interactions with engineering and meteorology.