Short answer
Islam does not fix one number. A person marries by their own choice once they reach puberty and maturity, and consummation is only allowed when the body is ready and no harm is done. Classical fiqh let a father contract a minor's nikah, but Hanafi scholars today advise marrying after maturity and keeping your country's legal minimum age.
Adulthood (bulugh) comes with the physical signs of puberty, or at fifteen lunar years if none appear, and an adult's nikah needs their own consent. The Hanafi books allow a guardian to contract a minor's nikah, with consummation forbidden until she can bear it without harm, but this is not encouraged, and state minimum age laws are to be kept.
Other madhhabs
- Shafi'i
- Only a father or paternal grandfather may marry off a minor girl, and only if she has never been married. Other guardians must wait until she is adult and agrees.
- Maliki
- Only the father may marry off a minor daughter. Other guardians must wait for her adulthood and consent.
- Hanbali
- Only the father, or an executor he appointed, may marry off a minor.
Explanation
People ask this for two reasons: to know when a young person may marry, and because of debates about history. The fiqh answer has three parts: when a person becomes an adult, whether a guardian may contract a child's nikah, and when a marriage may be consummated.
Adulthood. In the Hanafi school a person becomes an adult (baligh) with the signs of puberty: for a boy a wet dream or ejaculation, for a girl her first period or a pregnancy. If no sign appears, the fatwa is that adulthood begins at fifteen lunar years. From then on the person is accountable, and their own consent is needed for their nikah. The Quran links the end of guardianship to reaching marriageable age with sound judgement (4:6).
A guardian's contract. The classical books of all four schools allow a father to contract the nikah of a minor, based on the practice of the Companions and the marriage of Aisha narrated in Sahih al-Bukhari. The Hanafis also allow other guardians, and when someone other than the father or grandfather contracted it, the child may cancel it at puberty (khiyar al-bulugh). This was a permission, never a recommendation, and it never allowed harm: the girl stays with her family and the marriage is not consummated until she is physically able, judged by her health and not by a birthday.
Today. Hanafi scholars teach that a guardian must act only in the child's interest, and that a ruler may restrict something permitted for the public good. Most countries today set a legal minimum age for marriage, often eighteen, and Muslims must keep it. Marrying off a child against the law, or in a way that harms her, is sinful. On when young adults should marry, see marrying young.
The evidence
Quran, Surah An-Nisaa 4:6
وَٱبْتَلُوا۟ ٱلْيَتَٰمَىٰ حَتَّىٰٓ إِذَا بَلَغُوا۟ ٱلنِّكَاحَ فَإِنْ ءَانَسْتُم مِّنْهُمْ رُشْدًۭا فَٱدْفَعُوٓا۟ إِلَيْهِمْ أَمْوَٰلَهُمْ ۖ وَلَا تَأْكُلُوهَآ إِسْرَافًۭا وَبِدَارًا أَن يَكْبَرُوا۟ ۚ وَمَن كَانَ غَنِيًّۭا فَلْيَسْتَعْفِفْ ۖ وَمَن كَانَ فَقِيرًۭا فَلْيَأْكُلْ بِٱلْمَعْرُوفِ ۚ فَإِذَا دَفَعْتُمْ إِلَيْهِمْ أَمْوَٰلَهُمْ فَأَشْهِدُوا۟ عَلَيْهِمْ ۚ وَكَفَىٰ بِٱللَّهِ حَسِيبًۭا ﴿٦﴾
And test the orphans [in their abilities] until they reach marriageable age. Then if you perceive in them sound judgement, release their property to them. And do not consume it excessively and quickly, [anticipating] that they will grow up. And whoever, [when acting as guardian], is self-sufficient should refrain [from taking a fee]; and whoever is poor - let him take according to what is acceptable. Then when you release their property to them, bring witnesses upon them. And sufficient is Allah as Accountant.
Marriageable age and sound judgement mark the end of guardianship over property.
Sahih al-Bukhari 5136
Sahih... لا تنكح الأيم حتى تستأمر ولا تنكح البكر حتى تستأذن ...
"A previously married woman is not married off until she is consulted, and a virgin is not married off until her permission is sought."
An adult's consent is a condition of her marriage.
Sahih al-Bukhari 5065
Sahih... يا معشر الشباب من استطاع منكم الباءة فليتزوج ...
"O young people, whoever of you is able to marry, let him marry."
Marriage is tied to ability, physical and financial, not to a set age.
Where the ruling is recorded
- al-Hidaya, Kitab al-Nikah, Bab al-Awliya' wa al-Akfa'. A guardian may contract a minor's nikah, with the option of puberty when the guardian is not the father or grandfather.
- al-Durr al-Mukhtar with Radd al-Muhtar, Kitab al-Hajr, chapter on reaching adulthood. The signs of puberty, and fifteen years as the fatwa age when no sign appears.
- al-Mughni (Ibn Qudama), Kitab al-Nikah. The Hanbali view that only the father may marry off a minor.
Checked by our team. For a more accurate answer to your own situation, consult a scholar. Quran translation by Sahih International. Hadith Arabic from the standard editions of the six books and the Muwatta, with gradings as recorded there; the English is our own rendering. Spotted a mistake? Tell us.