APG stands for Ambulatory Patient Group, which is a classification system for outpatient services reimbursement developed for the American Medicare service by the Health Care Financing Administration. APGs are a part of Medicares prospective payment system for outpatient procedures and services. Unlike diagnosis-related group (DRG) reimbursement for inpatient care, which condenses medical events into one DRG, an outpatient visit may combine several APGs. An APG incorporates a group of outpatient procedures, ancillary services, or encounters that are similar and thus combined based on patient clinical characteristics and the resources expected.

APG is also the abbreviation for Aberdeen Proving Ground, a United States Army installation in Aberdeen, Maryland. However, in the context of healthcare, APG usually refers to the Ambulatory Patient Group.