Legal name is the name that identifies a person for legal, administrative and other official purposes. A person's first legal name generally is the name of the person that was given for the purpose of registration of the birth and which then appears on a birth certificate (see birth name), but may change subsequently. Most jurisdictions require the use of a legal name for all legal and administrative purposes, and some jurisdictions permit or require a name change to be recorded at marriage. The legal name may need to be used on various government issued documents (e.g., a court order). The term is also used when an individual changes his/her first or full name, typically after reaching a certain legal age (usually eighteen or over, though it can be as low as fourteen in several European nations).
A person's legal name typically is the same as his/her personal name, comprising a given name and a family name. The order varies according to culture and country. There are also country-by-country differences on changes of legal names by marriage. (See married name.)
Most countries require by law the registration of a name for newborn children, and some can refuse registration of "undesirable" names. In 1991, a Swedish couple refused to give their newborn a legal name, in protest of existing naming laws. In 1996, they were fined for not registering a name for their child for five years, after they unsuccessfully tried to register the child's name as Brfxxccxxmnpcccclllmmnprxvclmnckssqlbb11116, and then as "A".
The Civil Code of Quebec states that "Every person exercises his civil rights under the name assigned to him and stated in his act of birth," and spouses retain their legal names upon marriage. They can be changed, upon registration, only under prescribed conditions, and only where the person is a Canadian citizen who has been domiciled in Québec for at least one year. 
In Germany, names are regulated to a large extent. Apart from possibly adopting the partner's name upon marriage, German citizens may only change their name for a recognised important reason. Among other reasons, a change of names is permitted when the name can give rise to confusion, ridicule, unusual orthographic difficulties, or stigmatization. In certain situations, children's last names may also be changed to their natural, foster or adoptive parent's last name. Transsexuals may change their first names. Foreign names in writing systems that are not based on Latin are transliterated according to rules which may conflict with the system of transcribing or transliterating names that is used in the country of origin. Former titles of nobility became integrated into the last names in 1919 but continue to be adapted according to gender and other circumstances.
In the UK businesses that trade under names other than those of the owner or a corporate entity must display the name of owner and an address at which documents may be served, or the name and registered number of the corporate body and its registered address. The requirements apply to sole traders and partnerships, but there are special provisions for large partnerships where listing all partners would be onerous.
The information must be shown on any trading premises where the public have access to trade and in documents such as order forms, receipts and, as of January 2007, corporate websites (to be extended later in 2007 to sole trader websites).
In strict English law, if there is such a thing as a "legal" surname, it is easily changed. In the words of A dictionary of American and English law, "Any one may take on himself whatever surname or as many surnames as he pleases, without statutory licence". However, this does not apply to names given in baptism. As noted by Sir Edward Coke in Institutes of the Lawes of England, "a man may have divers names at divers times, but not divers Christian names."
Changes of name are usually effected through deed poll, enrolled either at the High Court of Justice or at the College of Arms, with a notice recorded in The London Gazette. Changes may also be made by means of a Royal License obtained through the College of Arms, with similar notice. While not a mandatory requirement, each is useful for having name changes registered in official documents.
Name changes must be recorded in the National Records of Scotland where a birth has been registered in Scotland, or where a person is the subject in Scotland of an entry in the Adopted Children Register, the Parental Order Register or the Gender Recognition Register. Only one change of name is allowed where a person has not yet reached the age of 16, and afterwards only one change of forename and three changes of surname may be granted during a person's lifetime, provided that at least five years have passed between changes of surname. Name changes may also be recorded where:
The above formalities are not necessary where a spouse/partner assumes the other spouse/partner's surname upon marriage or civil partnership, or reverts back to their original name upon separation, divorce or dissolution of the civil partnership.
A deed poll can also be used in Northern Ireland for this purpose.
Most states in the United States follow the common law which permits name changing for non-fraudulent purposes. This is actually the most common method, since most women who marry do not petition a court under the statutorily prescribed method, but simply use a new name (typically the husband's, a custom which started under the theory of coverture where a woman lost her identity and most rights when she married).
Most state courts have held that a legally assumed name (i.e., for a non-fraudulent purpose) is a legal name and usable as their true name, though assumed names are often not considered the person's technically true name.
The legal name of a business is the name under which the business conducts its operations.