A civil union is a legally and socially recognized union between partners of the same sex. As a socio-legal institution, civil unions were created to provide same-sex couples with many of the rights, benefits, and privileges typically associated with opposite-sex civil marriage. Civil unions are distinguished by the fact that they provide all of the state-recognized rights and benefits of marriage, without being the equivalent of marriage.

The term civil union was first adopted in the American context and, therefore, has a unique cultural, political, and historical trajectory. Given their particular development, it is important to distinguish civil unions from American-style domestic partnerships, European-style registered partnerships, and civil marriage.

Throughout the 1990s, but especially after the Hawaii Supreme Court's decision in Baehr v. Lewin (1993), ...