药理学（英语：Pharmacology），是研究药物与有机体（含病原体）相互作用及作用规律的学科。它既研究药物对生物的作用及作用机制，即药物效应动力学（Pharmacodynamics，简称药效学）；也研究药物在提提的影响下所发生的变化及其规律，即药物代谢动力学（Pharmacokinetics，简称药动学）。药理学是以基础医学中的生理学、生物化学、病理学、病理生理学、微生物学、免疫学、分子生物学等为基础，为防治疾病、合理用药提供基本理论、基础知识和科学思维方法，是基础医学、临床医学以及医学与药学的桥梁。

Pharmacology is the branch of medicine and biology concerned with the study of drug action, where a drug can be broadly defined as any man-made, natural, or endogenous (from within body) molecule which exerts a biochemical and/or physiological effect on the cell, tissue, organ, or organism (sometimes the word pharmacon is used as a term to encompass these endogenous and exogenous bioactive species). More specifically, it is the study of the interactions that occur between a living organism and chemicals that affect normal or abnormal biochemical function. If substances have medicinal properties, they are considered pharmaceuticals.