India's top court has ruled adultery is no longer a crime, striking down a 158-year-old colonial-era law which it said treated women as male property.
Previously any man who had sex with a married woman, without the permission of her husband, had committed a crime.
A petitioner had challenged the law saying it was arbitrary and discriminated against men and women.
It is not clear how many men have been prosecuted under the law - there is no data available.
This is the second colonial-era law struck down by India's Supreme Court this month - it also overturned a 157-year-old law which effectively criminalised gay sex in India.
While reading out the judgement on adultery, Chief Justice Dipak Misra said that while it could be grounds for civil issues like divorce, "it cannot be a criminal offence".
Who challenged the law?
Last August, Joseph Shine, a 41-year-old Indian businessman living in Italy, petitioned the Supreme Court to strike down the law. He argued that it discriminated against men by only holding them liable for extra-marital relationships, while treating women like objects.
"Married women are not a special case for the purpose of prosecution for adultery. They are not in any way situated differently than men," his petition said.
The law, Mr Shine said, also "indirectly discriminates against women by holding an erroneous presumption that women are the property of men".
In his 45-page petition, Mr Shine liberally quotes from American poet Ralph Waldo Emerson, women rights activist Mary Wollstonecraft and former UN Secretary General Kofi Annan on gender equality and the rights of women.
Where else is adultery a criminal offence?
Adultery is considered illegal in 21 American states, including New York, although surveys show that while most Americans disapprove of adultery, they don't think of it as a crime.
"The criminal statutes remain in force for largely symbolic reasons, and there isn't enough enforcement risk for anyone to incur the political costs of repealing them," Deborah Rhode, a professor of law at Stanford University and the author of Adultery: Infidelity and the Law told the BBC.
Adultery is prohibited in Sharia or Islamic Law, so it is a criminal offence in Islamic countries such as Iran, Saudi Arabia, Afghanistan, Pakistan, Bangladesh and Somalia.
Taiwan punishes adultery by up to a year in prison and it is also deemed a crime in Indonesia. In fact, Indonesia is drafting laws that prohibit all consensual sex outside the institution of marriage.
In 2015, South Korea's Supreme Court struck down a similar law where a man could be sent to prison for two years or less for adultery. The court said the law violated self-determination and privacy.
More than 60 countries around the world had done away with laws that made adultery a crime, according to Indian lawyer Kaleeswaram Raj.
In the UK, adultery is not a criminal offence and like many other countries, one of the main reasons given for divorce.
Couples cannot use adultery as a ground for divorce if they lived together as a couple for six months after the infidelity was known about.
Have there been previous challenges to the law?
In 1954, the law was first challenged by a petitioner asking why women cannot be punished for the offence, and that such "exemption was discriminatory".
The Supreme Court rejected the plea.
Since then, the top court has rejected similar pleas, including the constitutional validity of the law, at least twice - 1985 and 1988.
"The stability of marriage is not an ideal to be scorned," a judge said in 1985.
A married woman had approached the court, demanding the right to file a complaint of adultery against her husband's unmarried lover. The court, rather patronisingly, described the plea as a "crusade by a woman against a woman".
It said the law was about punishing the "outsider" who "breaks into the matrimonial home" and "violates its sanctity".
Two different panels on law reforms in 1971 and 2003 recommended that women should also be prosecuted for the offence.
"The society abhors marital infidelity. Therefore there is no good reason for not meting out similar treatment to the wife who has sexual intercourse with a married man," the 2003 panel, led by a judge, said.
In 2011, the top court, hearing another plea, said the law was facing criticism for "showing a strong gender bias, it makes the position of a married woman almost as a property of her husband".
What has the reaction been to the latest ruling?
Many Indians were not even aware the law existed. However, after Thursday's ruling, people have been largely supportive of the verdict.