嗅觉系统是指感受气味的感受系统。大部份哺乳类及爬虫类动物的嗅觉系统由主要嗅觉系统（main olfactory system）及辅助嗅觉系统（accessory olfactory system）组成，前者负责感应气态物质的气味，后者则负责感应液态物质的气味。大多数行为研究表明辅助嗅觉系统接受的气味通常是信息激素。
谈及嗅觉系统，我们通常会联系到同样是化学性感受的味觉系统，因为两者都将化学信号转化为感受。

The olfactory system is the sensory system used for olfaction, or the sense of smell. Most mammals and reptiles have two distinct parts to their olfactory system: a main olfactory system and an accessory olfactory system. The main olfactory system detects volatile, airborne substances, while the accessory olfactory system senses fluid-phase stimuli. Behavioral evidence indicates that most often, the stimuli detected by the accessory olfactory system are pheromones.