Fentanyl is a strong opioid medication primarily used medically for the treatment of severe pain. It is used in various forms for acute pain such as major trauma or surgery, as well as for severe chronic pain including cancer- related pain. It acts by interrupting pain signals between the brain and the body, providing effective pain relief. Fentanyl is used in anesthesia (both for induction and maintenance), regional anesthesia, obstetrics, breakthrough cancer pain, and palliative care. It can be administered via injection, transdermal patches, sublingual forms, and other routes depending on the clinical situation. It is also used to relieve severe shortness of breath when morphine is not suitable, especially in palliative care settings. Because of its potency and risk, fentanyl must be prescribed and used carefully under medical supervision.