The Civil Partnership Act comes into effect in the United Kingdom, and the first civil partnership is registered there.

The Civil Partnership Act 2004 is an Act of the Parliament of the United Kingdom, introduced by the Labour government, which grants civil partnerships in the United Kingdom the rights and responsibilities very similar to those in civil marriage. Initially the Act permitted only same-sex couples to form civil partnerships. This was altered to include opposite-sex couples in 2019. Civil partners are entitled to the same property rights as married couples, the same exemption as married couples regarding social security and pension benefits, and also the ability to exercise parental responsibility for a partner's children, as well as responsibility for reasonable maintenance of one's partner and their children, tenancy rights, full life insurance recognition, next-of-kin rights in hospitals, and others. There is a formal process for dissolving civil partnerships, akin to divorce.

Civil partnership in the United Kingdom is a form of civil union between couples open to both same-sex couples and opposite-sex couples. It was introduced via the Civil Partnership Act 2004 by the Labour government. The Act initially permitted only same-sex couples to form civil partnerships, but the law was expanded to include different-sex couples in 2019.