Interfaith marriage, traditionally called "mixed marriage", is marriage between spouses professing different religions. Although interfaith marriages are most often contracted as civil marriages, in some instances they may be contracted as a religious marriage. This depends on religious prohibitions against the marriage by the religion of one (or both) spouses, based on religious doctrine or tradition.
In an interfaith marriage, each partner typically adheres to their own religion; this excludes a marriage of a spouse belonging to religion X to a spouse who has undergone religious conversion from religion Y to religion X. Interfaith marriage is also distinct from the concepts of religious assimilation, cultural assimilation, religious disaffiliation, and apostasy. Despite the distinction, these issues are associated with aspects of interfaith marriage. Interfaith marriage is also distinct from interracial and inter-ethnic marriage (also known as "mixed marriage"), since spouses in an interfaith marriage may share the same race or ethnicity.
In some religions, religious doctrine prohibits interfaith marriage. In others, religious tradition opposes interfaith marriage but may allow it in limited circumstances. Several major religions are mute on the issue, and still others allow it with requirements for ceremony and custom. For ethno-religious groups, resistance to interfaith marriage may be a form of self-segregation.
According to Article 16 of the Universal Declaration of Human Rights, men and women who have attained the age of majority have the right to marry "without any limitation due to race, nationality or religion". Although most of Article 16 is incorporated verbatim in Article 23 of the International Covenant on Civil and Political Rights, the references to religious and racial limitations is omitted. Article 17, clause two of the American Convention on Human Rights says that all men and women have the right to marry, subject to the conditions of domestic law "insofar as such conditions do not affect the principle of nondiscrimination established in this Convention."