Irreligion (adjective form: non-religious or irreligious) is the absence, indifference, rejection of, or hostility towards religion.

When characterized as the rejection of religious belief, it encompasses atheism, agnosticism, religious dissidence, and secular humanism. When characterized as the absence of religious belief, it may also include "spiritual but not religious", pandeism, ignosticism, nontheism, pantheism, panentheism, and freethought. When characterized as indifference to religion, it is known as apatheism. When characterized as hostility towards religion, it encompasses antitheism and/or antireligion.