Secularism is the principle of seeking to conduct human affairs based on secular, naturalistic considerations.

Secularism is most commonly defined as the separation of religion from civil affairs and the state, and may be broadened to a similar position seeking to remove or to minimize the role of religion in any public sphere. The term "secularism" has a broad range of meanings, and in the most schematic, may encapsulate any stance that promotes the secular in any given context. It may connote anti-clericalism, atheism, naturalism, non-sectarianism, neutrality on topics of religion, or the complete removal of religious symbols from public institutions.

As a philosophy, secularism seeks to interpret life based on principles derived solely from the material world, without recourse to religion. It shifts the focus from religion towards "temporal" and material concerns.

There are distinct traditions of secularism in the West, like the French, Turkish and Anglo-American models, and beyond, as in India, where the emphasis is more on equality before law and state neutrality rather than blanket separation. The purposes and arguments in support of secularism vary widely, ranging from assertions that it is a crucial element of modernization, or that religion and traditional values are backward and divisive, to the claim that it is the only guarantor of free religious exercise.