法定最低结婚年龄，又称法定结婚年龄或适婚年龄，是指一个人被允许有权利（或经过父母同意或以其他形式）结婚的年龄。法定结婚年龄的标准因为国家或地区的不同而异，不过通常而言一般在18岁左右，但也有的国家或地区在有父母同意和/或法律许可或怀孕的情况下，允许人们在更年轻的年龄结婚。法定结婚年龄不能与法定成年人年龄、最低合法性交年龄、或某些地区的实际初次结婚年龄相互混淆，因为在发展中国家，童婚非常普遍。

1962年，55个缔约国签署《关于婚姻的同意、结婚最低年龄及婚姻登记的公约》，该条约要求各方通过立法明确规定结婚最低年龄，从而凌驾于习惯法、宗族和部落的法律 。

Marriageable age (or marriage age) is the age at which a person is allowed by law to marry, or either as a right or subject to parental or other forms of consent. Age and other prerequisites to marriage vary between jurisdictions, but generally is set at eighteen. Until recently, the marriageable age for girls was lower in many jurisdictions than for boys, but in many places has now been raised to those of boys to further gender equality. Most jurisdictions allow marriage at a younger age with parental or judicial approval, and some also allow younger people to marry if the girl is pregnant. The marriage age should not be confused with the age of majority or the age of consent, though in some places they may be the same. In many developing countries, the official age prescriptions stand as mere guidelines. In some societies, a marriage by a person (usually a girl) below the age of 18 is regarded as a child marriage.