药物（英语：Drug）广义上指可以对人或其他动物产生已知生物效应的物质。食物通常不适用于这个定义，尽管它们可以对生物物种产生生理效应。

药理学上，药物指用于预防、治疗、诊断疾病或增强体格或改善精神状态的化学物质。 药品可以短期使用或定期使用来治疗慢性疾病。

精神药物是可以影响神经系统功能，改变感觉、情绪、意识的化学物质。 酒精、尼古丁和咖啡是世界上使用最广泛的精神药物。

娱乐性药物是没有医疗用途，而是用来获得快感的药物。 常见的娱乐性药物包括酒精、尼古丁和咖啡因，也包括其他物质如鸦片类药物和安非他命。

A drug is any substance other than food, that when inhaled, injected, smoked, consumed, absorbed via a patch on the skin or dissolved under the tongue causes a physiological change in the body.

In pharmacology, a pharmaceutical drug or medicine, is a chemical substance used to treat, cure, prevent, diagnose a disease or promote well-being. Traditionally drugs were obtained through extraction from medicinal plants, but more recently also by organic synthesis. Pharmaceutical drugs may be used for a limited duration, or on a regular basis for chronic disorders.