A package insert is a document included in the package of a medication that provides information about that drug and its use. For prescription medications, the insert is technical, providing information for medical professionals about how to prescribe the drug. Package inserts for prescription drugs often include a separate document called a "patient package insert" with information written in plain language intended for the end-user—the person who will take the drug or give the drug to another person, such as a minor. Inserts for over-the-counter medications are also written plainly.

In the United States, labelling for the healthcare practitioner is called "Prescribing Information" (PI), and labelling for patients and/or caregivers includes "Medication Guides", "Patient Package Inserts", and "Instructions for Use". In Europe, the technical document is called the "summary of product characteristics" (SmPC), and the document for end-users is called the "patient information leaflet" (PIL) or "package leaflet".

Similar documents attached to the outside of a package are sometimes called outserts.