Chapter XVI, Section 377 of the Indian Penal Code is a piece of legislation in India introduced during British rule of India that criminalises unnatural sexual activity. It was declared unconstitutional by the High Court of Delhi on 2 July 2009.

The Indian Penal Code (IPC), of which Section 377 forms a part, was drafted in 1860 by Lord Macaulay as a part of the colonial project of regulating and controlling the British and Indian-origin subjects. It reads:

377. Unnatural offences: Whoever voluntarily has carnal intercourse against the order of nature with any man, woman or animal, shall be punished with imprisonment for life, or with imprisonment of either description for term which may extend to ten years, and shall also be liable to fine.

The ambit of Section 377, which was devised to criminalize and prevent homosexual associations.

Convictions are extremely rare, and in the last twenty years there have been no convictions for homosexual relations in India. However, Human Rights Watch argues that the law has been used to harass HIV/AIDS prevention efforts, as well as sex workers, men who have sex with men, and other groups at risk of the disease. The People's Union for Civil Liberties has published two reports of the rights violations faced by sexual minorities and, in particular, transsexuals in India.

In 2006 it came under criticism from 100 Indian literary figures, most prominently Vikram Seth. The law subsequently came in for criticism from several ministers, most prominently Anbumani Ramadoss and Oscar Fernandes. In 2008, a judge of the Bombay High Court also called for the scrapping of the law.

The movement to repeal Section 377 has been led by the Naz Foundation India Trust, an activist group, which filed a public interest litigation in the Delhi High Court in 2001, seeking legalisation of homosexual intercourse between consenting adults.

In a historic judgement, on 2 Jul 2009, Delhi High Court overturned the 150 year old section, legalising consensual homosexual activities between adults. The essence of the section goes against the fundamental right of human citizens, stated the high court while striking it down. In a 105-page judgement, a bench of Chief Justice Ajit Prakash Shah and Justice S Muralidhar said that if not amended, section 377 of the IPC would violate Article 21 of the Indian constitution, which states that every citizen has equal opportunity of life and is equal before law.

The two judge bench went on to hold that:

Any kind of discrimination is antithesis of right to equality, said the court, while allowing plea of gay rights activists for decriminalization of homosexuality.

The court stated that the judgement would hold until Parliament chose to amend the law. However, the judgement keeps intact the provisions of Section 377 insofar as it applies to non-consensual non-vaginal intercourse and intercourse with minors.