Christian mortalism is the Christian belief that the human soul is not naturally immortal and may include the belief that the soul is "sleeping" after death until the Resurrection of the Dead and the Last Judgment, a time known as the intermediate state. "Soul sleep" is often used as a pejorative term, so the more neutral term "mortalism" was also used in the nineteenth century, and "Christian mortalism" since the 1970s.

Historically the term psychopannychism was also used, despite problems with the etymology and application. The term thnetopsychism has also been used; for example, Gordon Campbell (2008) identified John Milton as believing in the latter.

This viewpoint stands in contrast with the traditional Christian belief that immortal souls immediately go to heaven, hell, or purgatory after death. Christian conditionalism has been taught by several theologians and church organizations throughout history while also facing opposition from aspects of Christian organized religion. The Catholic Church condemned such thinking in the Fifth Council of the Lateran as "erroneous assertions". Supporters include the sixteenth-century religious figure Martin Luther and the eighteenth-century religious figure Henry Layton, among many others.