Hospital-acquired infections (or healthcare-associated infections) are infections that occur after a patient is admitted to a hospital or any healthcare facility and that were not present at the time of admission.

An infection is usually defined as hospital-acquired or healthcare-associated if it occurs >48 hours after admission to the healthcare facility. Common hospital-acquired infections include central line- or peripheral catheter-associated bloodstream infections, catheter-associated urinary tract infections, hospital-acquired pneumonia (HAP), ventilator-associated pneumonia (VAP), and surgical site infections.