In anatomy of the digestive system, the ileum (not to be confused with the ilium), is the final section of the small intestine. It is about 4m long in humans, follows the jejunum and is separated from the cecum by the iliocecal valve ( abbreviated as ICV).

Its function is to absorb vitamin B₁₂ and bile salts.

In the fetus the ileum is connected to the navel by a duct. In some humans this duct fails to close after birth and causes a condition called Meckel's diverticulum.