In pharmacology, hazardous drugs are drugs that are known to cause harm, which may or may not include genotoxicity (the ability to cause a change or mutation in genetic material).

The National Institute for Occupational Safety and Health (NIOSH) considers a drug to be hazardous if it exhibits one or more of the following characteristics in humans or animals: carcinogenicity, teratogenicity or developmental toxicity, reproductive toxicity, organ toxicity at low doses, genotoxicity, or structure and toxicity profiles of new drugs that mimic existing hazardous drugs.

Antineoplastic cytotoxic medications, anesthetic agents, anti-viral agents, and others, have been identified as hazardous. These hazardous medications are capable of causing serious effects including cancer, organ toxicity, fertility problems, genetic damage, and birth defects.