Olfaction (also known as olfactics; adjectival form: "olfactory") is the sense of smell. This sense is mediated by specialized sensory cells of the nasal cavity of vertebrates, and, by analogy, sensory cells of the antennae of invertebrates. Many vertebrates, including most mammals and reptiles, have two distinct olfactory systems—the main olfactory system, and the accessory olfactory system (used mainly to detect pheromones). For air-breathing animals, the main olfactory system detects volatile chemicals, and the accessory olfactory system detects fluid-phase chemicals. Olfaction, along with taste, is a form of chemoreception. The chemicals themselves that activate the olfactory system, in general at very low concentrations, are called odorants. Although taste and smell are separate sensory systems in land animals, water-dwelling organisms often have one chemical sense.

Die olfaktorische Wahrnehmung (lat. olfacere „riechen“), auch Geruchssinn, olfaktorischer Sinn oder Riechwahrnehmung, bezeichnet die Wahrnehmung von Gerüchen. Der komplexe Geruchssinn wird erforscht von der Osmologie oder auch Osphresiologie.

L’olfaction ou l’odorat est le sens qui permet d'analyser les substances chimiques volatiles (odeurs) présentes dans l’air. Ce sens est certainement le moins utilisé par l’être humain, à la différence de nombreux mammifères pour lesquels il est prépondérant.

Luktsinnet är det sinne som gör att vi kan känna olika lukter, odörer och dofter. De sinnesceller som registrerar doftmolekylerna sitter samlade i ett litet organ högst upp i nästaket, area olfactoria.

Węch to jeden z dwóch, oprócz smaku, zmysłów chemicznych.