In cultures that practice marital monogamy, bigamy is the act of entering into a marriage with one person while still legally married to another. Bigamy is a crime in most western countries, and when it occurs in this context often neither the first nor second spouse is aware of the other. In countries that have bigamy laws, consent from a prior spouse makes no difference to the legality of the second marriage, which is usually considered void.
Before Christianity became the official religion of the Roman Empire, Diocletian and Maximilian passed strict anti-polygamy laws in 285 AD that mandated monogamy as the only form of legal marital relationship, as had traditionally been the case in classical Greece and Rome. In 393, the Byzantine Emperor Theodosius I issued an imperial edict to extend the ban on polygamy to Jewish communities. In 1000, Rabbi Gershom ben Judah ruled polygamy inadmissible within Ashkenazi Jewish communities, living in a Christian environment.
According to feminist historian Sarah McDougall, the Christian European insistence on monogamy and its enforcement arose as a consequence of 16th Century Islamic incursions into Central Europe and the advent of European colonialism within the Americas, Africa and Asia, which exposed European Christians to cultures that practised polygamy. As a consequence, nominal Christian male bigamists were subjected to unprecedented harsh punishments, such as execution, galley servitude, exile, and prolonged imprisonment. McDougall argues that female bigamists were not as harshly punished due to women's perceived inferiority and absence of moral agency.
Most western countries do not recognize polygamous marriages, and consider bigamy a crime. Several countries also prohibit people from living a polygamous lifestyle. This is the case in some states of the United States where the criminalization of a polygamous lifestyle originated as anti-Mormon laws, although they are rarely enforced.
In diplomatic law, consular spouses from polygamous countries are sometimes exempt from a general prohibition on polygamy in host countries. In some such countries, only one spouse of a polygamous diplomat may be accredited, however.
China: Illegal (but tolerated for some minorities, such as Tibetans, in some rural areas in the South West) .
Colombia Illegal with exceptions (such as religion). Although bigamy no longer exists as a lone figure in the Colombian judicial code marrying someone new without dissolving an earlier marriage may yield to other felonies such as civil status forgery or suppression of information.
Republic of Ireland: Bigamy is a statutory offence. It is committed by a person who, being married to another person, goes through a ceremony capable of producing a valid marriage with a third person. The offence is created by section 57 of the Offences against the Person Act 1861. This section replaces section 26 of the Act 10 Geo. 4 c. 34 for the Republic of Ireland.
Malaysia: Permitted for Muslims; required to obtain judicial consent, show financial capability, and several strict conditions. Some variation in law between states (family law relating to non-Muslims is under federal jurisdiction).
Malta: Illegal under the Marriage Act of 1975, section 6.
Netherlands: Illegal. Up to 6 years imprisonment. If the new partner is aware of the bigamy he or she can be imprisoned for a maximum of 4 years.
New Zealand: Illegal under section 205 of the Crimes Act 1961. Up to 7 years imprisonment, or up to 2 years imprisonment if the judge is satisfied the second spouse was aware their marriage would be void.
Morocco: Permitted for Muslims, restrictions apply.
Thailand: Polygamy in Thailand Prior to October 1, 1935 polygamy could be freely practiced and recognised under civil law in Thailand. The old family law divided wives into three categories, all in accordance of the way in which they would become wives. There were three categories for a polygamous marriage, the first called "Mia Glang Muang," who would be the "official wife" that the husband's parents had "acquired for him," the second known as "Mia Glang Norng," the "minor wife" whom the man attained after his first marriage, and the third, "Mia Glang Tasee," the title given to slave wives that were purchased from the mother and father of their prior owners. While polygamy has since been abolished, it is still very much alive in Thailand, and according to reports, widely accepted. Even still, such unions are not recognised under Thai law as in accordance with the law that states "A man or a woman cannot marry each other while one of them has a spouse."
In the United Kingdom a person guilty of bigamy is liable, on conviction on indictment, to imprisonment for a term not exceeding seven years, or on summary conviction to imprisonment for a term not exceeding six months, or to a fine not exceeding the prescribed sum, or to both.