Pharmacology (in Greek: pharmacon (φάρμακον) meaning drug, and logos (λόγος) meaning science) is the study of how chemical substances interact with living systems. If substances have medicinal properties, they are considered pharmaceuticals. The field encompasses drug composition and properties, interactions, toxicology, therapy, and medical applications and antipathogenic capabilities. The science is considered to have been invented by Arab physicians in Baghdad during the Golden Age of Islam; pharmacopoeias were penned in Arabic as early as the 7th century (Amin A. Khairallah: Outline of Arabic Contributions to Medicine: Chapter X, Chemistry and Pharmacy. 1946, ).

Development of medication is a vital concern to medicine, but also has strong economical and political implications. To protect the consumer and prevent abuse, many governments regulate the manufacture, sale, and administration of medication. In the United States, the main body that regulates pharmaceuticals is the Food and Drug Administration and they enforce standards set by the United States Pharmacopoeia.

Pharmacology as a science is practiced by pharmacologists. Subdisciplines are clinical pharmacology (the medical field of medication effects on humans), neuro- and psychopharmacology (effects of medication on behavior and nervous system functioning), and theoretical pharmacology.