Morphine and fentanyl are both opioid analgesic drugs, meaning that they relieve pain by binding to structures called opioid receptors in the cells of the nervous system. Morphine is a naturally occurring opioid substance, or opiate, derived from opium poppy plants, or Papaver somniferum, while fentanyl is synthetic. Fentanyl is much more potent than morphine, and while some of their medical uses overlap, each has its own distinct applications.