Is it allowed to marry a cousin?

What the Qur'an permits

The permission is not a loophole or a concession to custom. It is stated in the Qur'an itself, in the verse addressing the Prophet ﷺ:

"…and the daughters of your paternal uncles and the daughters of your paternal aunts, and the daughters of your maternal uncles and the daughters of your maternal aunts…"— Qur'an 33:50

The Permanent Committee (fatwa 6160) addresses the obvious question: the verse opens by addressing the Prophet ﷺ, so does it apply to everyone else? Their answer is that it does. The rule in the Shari'ah is that when a command is addressed to the Prophet ﷺ, the community is included in it unless a text shows the ruling is his alone — and this verse does exactly that at its end, where Allah says of the woman who offers herself in marriage, "exclusively for you, not for the believers." That phrase marks the exception; the rest of the verse remains general.

Why the scholars call this the middle path

Ibn Kathir's comment, quoted by IslamWeb (fatwa 64640), explains the wisdom: the law here is a middle course between two extremes. Christian practice at the time restricted marriage unless the man and woman were separated by seven forefathers or more; Jewish practice permitted a man to marry his brother's daughter. The complete Shari'ah abolished both excesses — it permitted the cousin, and it forbade what the Jews permitted.

"This is a just middle course between excess and neglect… the complete and pure Shari'ah came to demolish the excess of the Christians by permitting the daughter of the paternal uncle and aunt and the daughter of the maternal uncle and aunt, and to forbid what the Jews fell short in by permitting the daughter of the brother and sister — and this is an ugly, dreadful thing."— Ibn Kathir, quoted in IslamWeb fatwa 64640

How far the permission reaches

The permission is not limited to your own generation's cousins. Shaykh Ibn Baz (fatwa 9472) lists it out: the daughter of your paternal uncle, the daughter of your father's paternal uncle, the daughter of your grandfather's paternal uncle, the daughter of your maternal uncle, the daughter of your mother's maternal uncle, the daughter of your grandmother's or grandfather's maternal uncle — all of them are permitted. IslamWeb (fatwa 64640) adds that the daughter of your father's paternal uncle falls under the same ruling, and (fatwa 39790) that the granddaughter of your paternal aunt is likewise permitted, since no text forbids her.

• It applies to all four lines: paternal uncle, paternal aunt, maternal uncle, maternal aunt — and their descendants, however far down.
• It applies to both men and women: the ruling is stated for a man marrying these relatives; the same relatives are permitted to him and he to them.
• It is not affected by how the family is related otherwise: Ibn Baz was asked about a woman who is at once his paternal uncle's daughter and his maternal aunt's daughter — he answered that this too is permitted.

What is forbidden instead

The prohibition falls on a different category, and Ibn Baz states it plainly and repeatedly: your aunt, your sister, and your niece are forbidden — by explicit text and by the agreement of the scholars. The Permanent Committee and IslamWeb give the same list.

• Your sister, and her daughters however far down.
• Your paternal or maternal aunt ('ammah / khalah), and the aunt of your aunt however far up.
• Your niece — the daughter of your brother or sister, however far down.
• A woman and her aunt together: you may not be married to a woman and, at the same time, to her paternal or maternal aunt. Ibn Baz (fatwa 19033) grounds this in the Prophet's ﷺ prohibition of combining a woman and her aunt, and notes that the scholars cited here hold its prohibition. But if the aunt has died, or the marriage ended and the waiting period is over, marrying the niece becomes permissible, because the forbidden combination no longer exists.
• Relatives by nursing: IslamWeb (fatwa 64640) attaches the condition that the permission holds "if there is no barrier from the side of nursing." A woman who is your sister or aunt through breastfeeding is in the same category as one who is so by blood.

If custom stands in the way

Some families treat marriage to a cousin as forbidden by tradition. IslamWeb (fatwa 31254) addresses this directly: since the scholars are agreed that marrying the paternal uncle's daughter and the like is permitted, it may not be prevented on the basis of a custom followed in a country or a tribe. The fatwa cites the verse,

"Or have they partners who have ordained for them a religion which Allah has not permitted?" (Qur'an 42:21)

and the command not to forbid the good things Allah has made lawful (Qur'an 5:87).

The same fatwa advises a son whose father objects to try to persuade him and keep him pleased, because the pleasure of the Lord is in the pleasure of the parent — and if the father still refuses, leaving the marriage may be closer to honouring him. The permission is a ruling about what is lawful, not a command to marry a particular person.

Key takeaways

• Marrying a cousin is permitted, and the scholars are agreed on it; the evidence is Qur'an 33:50.
• The permission covers all four lines — paternal uncle, paternal aunt, maternal uncle, maternal aunt — and their descendants, however far down.
• Your sister, your aunt and your niece remain forbidden, by explicit text and scholarly agreement.
• You may not be married to a woman and her aunt at the same time; if the first marriage ends or the aunt dies, the barrier is lifted.
• A barrier by nursing changes the ruling, so check that before proceeding.
• No local custom may forbid what Allah has permitted, though a parent's wishes should still be handled with kindness.

Further reading

• Shaykh Ibn Baz, Majmu' al-Fatawa wa al-Maqalat — the sections on marriage to the daughter of the paternal uncle and aunt.
• al-Mughni of Ibn Qudamah, on the women forbidden in marriage.
• Ibn 'Abd al-Barr, al-Kafi fi Fiqh Ahl al-Madinah, the chapter on the prohibition of marrying relatives by lineage and marriage.

And Allah knows best.