Morphine and fentanyl are both opioid analgesics, but fentanyl is far more potent—about 50–100 times stronger than morphine. Morphine has a slower onset and longer duration, making it suitable for sustained pain relief, while fentanyl acts rapidly and is often used in acute or surgical settings. Fentanyl carries a higher risk of overdose due to its potency. Both can cause respiratory depression, dependence, and other typical opioid side effects.