Short answer
No, divorce is not a sin in itself. It is allowed when a marriage cannot work, but it is disliked without real need, and it becomes sinful when done to harm a spouse or in the forbidden ways, such as during her period or three at once. The four schools agree.
Talaq is permitted for need and disliked without it. The sunnah way is one talaq in a clean period without intimacy; talaq during her period, or three at once, is a sinful (bid'i) talaq even though it takes effect.
The four schools agree on this.
Explanation
Allah legislated divorce in the Quran, named a whole surah after it, and set out how to do it with dignity (2:229, 65:1). Companions divorced and remarried, and no shame was attached to it. So divorce is not a sin, and divorced men and women should never be looked down on.
But divorce has a cost. It breaks a covenant and affects children. The Prophet ﷺ described Shaytan sending out his troops and praising most the one who says, "I did not leave him until I had separated him from his wife." A well known narration calls divorce the most hated of lawful things to Allah. Many hadith scholars grade its chain weak, but its meaning matches the other evidence.
- Not sinful: divorce for a real need, after trying to repair the marriage.
- Disliked: divorce on a whim or without reason.
- Sinful: divorce intended to harm her (2:231), talaq during her period or after intimacy in a clean period, three talaqs at once, and withholding her mahr or iddah rights.
- For the wife: asking for divorce without a real reason is condemned, but with a real reason it is her right to seek it. See khula.
- Sometimes better: when staying together means ongoing harm or sin, separation can be the more pious choice.
If you are considering divorce, read valid reasons for divorce and the divorce process, and speak to a mufti or counsellor first.
The evidence
Quran, Surah Al-Baqara 2:229
ٱلطَّلَٰقُ مَرَّتَانِ ۖ فَإِمْسَاكٌۢ بِمَعْرُوفٍ أَوْ تَسْرِيحٌۢ بِإِحْسَٰنٍۢ ۗ وَلَا يَحِلُّ لَكُمْ أَن تَأْخُذُوا۟ مِمَّآ ءَاتَيْتُمُوهُنَّ شَيْـًٔا إِلَّآ أَن يَخَافَآ أَلَّا يُقِيمَا حُدُودَ ٱللَّهِ ۖ فَإِنْ خِفْتُمْ أَلَّا يُقِيمَا حُدُودَ ٱللَّهِ فَلَا جُنَاحَ عَلَيْهِمَا فِيمَا ٱفْتَدَتْ بِهِۦ ۗ تِلْكَ حُدُودُ ٱللَّهِ فَلَا تَعْتَدُوهَا ۚ وَمَن يَتَعَدَّ حُدُودَ ٱللَّهِ فَأُو۟لَٰٓئِكَ هُمُ ٱلظَّٰلِمُونَ ﴿٢٢٩﴾
Divorce is twice. Then, either keep [her] in an acceptable manner or release [her] with good treatment. And it is not lawful for you to take anything of what you have given them unless both fear that they will not be able to keep [within] the limits of Allah. But if you fear that they will not keep [within] the limits of Allah, then there is no blame upon either of them concerning that by which she ransoms herself. These are the limits of Allah, so do not transgress them. And whoever transgresses the limits of Allah - it is those who are the wrongdoers.
Divorce is allowed, with kindness.
Quran, Surah At-Talaaq 65:1
بِسْمِ ٱللَّهِ ٱلرَّحْمَٰنِ ٱلرَّحِيمِ يَٰٓأَيُّهَا ٱلنَّبِىُّ إِذَا طَلَّقْتُمُ ٱلنِّسَآءَ فَطَلِّقُوهُنَّ لِعِدَّتِهِنَّ وَأَحْصُوا۟ ٱلْعِدَّةَ ۖ وَٱتَّقُوا۟ ٱللَّهَ رَبَّكُمْ ۖ لَا تُخْرِجُوهُنَّ مِنۢ بُيُوتِهِنَّ وَلَا يَخْرُجْنَ إِلَّآ أَن يَأْتِينَ بِفَٰحِشَةٍۢ مُّبَيِّنَةٍۢ ۚ وَتِلْكَ حُدُودُ ٱللَّهِ ۚ وَمَن يَتَعَدَّ حُدُودَ ٱللَّهِ فَقَدْ ظَلَمَ نَفْسَهُۥ ۚ لَا تَدْرِى لَعَلَّ ٱللَّهَ يُحْدِثُ بَعْدَ ذَٰلِكَ أَمْرًۭا ﴿١﴾
O Prophet, when you [Muslims] divorce women, divorce them for [the commencement of] their waiting period and keep count of the waiting period, and fear Allah, your Lord. Do not turn them out of their [husbands'] houses, nor should they [themselves] leave [during that period] unless they are committing a clear immorality. And those are the limits [set by] Allah. And whoever transgresses the limits of Allah has certainly wronged himself. You know not; perhaps Allah will bring about after that a [different] matter.
Divorce has a proper way, and leaving it is what makes it sinful.
Sahih Muslim 2813
Sahih... ما تركته حتى فرقت بينه وبين امرأته ...
"I did not leave him until I had separated him from his wife."
Breaking up a marriage is what Shaytan loves most, so divorce should not be taken lightly.
Sunan Abi Dawud 2226
Graded sahih... أيما امرأة سألت زوجها طلاقا في غير ما بأس فحرام عليها رائحة الجنة ...
"Any woman who asks her husband for a divorce without a real reason, the scent of Paradise is forbidden to her."
Divorce without reason is condemned, which implies that a real reason is accepted.
Where the ruling is recorded
- Radd al-Muhtar (Ibn Abidin), Kitab al-Talaq, opening discussion. The basic rule in talaq is prohibition, lifted when there is a need.
- al-Hidaya, Kitab al-Talaq, Bab Talaq al-Sunnah. The sunnah and the bid'i forms of talaq.
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.