The part of the body that is involved in the detection of smells which consist of a group of sensory receptors that respond to air-borne or water-borne chemicals: Vertebrates possess a pair of olfactory organs in the mucous membrane lining the upper part of the nose, which opens to the exterior via the external nostrils.

Chemicals from the environment are dissolved in the mucus secreted by the olfactory organs and is transmitted to the brain by the receptors via the olfactory nerve.

Olfactory organs are found on the antennae in insects and in various positions in other invertebrates.