Sati or suttee is a Hindu practice in which a widow burns alive on her deceased husband's funeral pyre, either voluntarily, by coercion, or by a perception of the lack of satisfactory options for continuing to live. Although it is debated whether it received scriptural mention in early Hinduism, it has been linked to related Hindu practices in the Indo-Aryan-speaking regions of India, which have diminished the rights of women, especially those to the inheritance of property. A cold form of sati, or the neglect and casting out of Hindu widows, has been prevalent from ancient times.

Greek sources from around c. 300 BCE make isolated mention of sati, but it probably developed into a real fire sacrifice in the medieval era. In the early 19th century, the British East India Company, in the process of extending its rule to most of India, initially tried to stop the innocent killing; William Carey, a British Christian evangelist, noted 438 incidents within a 30-mile (48-km) radius of the capital, Calcutta, in 1803, despite its ban within Calcutta. Between 1815 and 1818, the number of documented incidents of sati in Bengal Presidency doubled from 378 to 839. Opposition to the practice of sati by evangelists like Carey, and by Hindu reformers such as Raja Ram Mohan Roy ultimately led the British Governor-General of India Lord William Bentinck to enact the Bengal Sati Regulation, 1829, declaring the practice of burning or burying alive of Hindu widows to be punishable by the criminal courts. Following the ban, hundreds of Hindus appealed against the ban on the practice but were unsuccessful. The ban on Sati practice was upheld by the Privy council in 1832.

Isolated incidents of sati were recorded in India in the late 20th century, leading the Government of India to promulgate the Sati (Prevention) Act, 1987, criminalising the aiding or glorifying of sati.

The practice is named after the Hindu goddess Sati, who is believed to have self-immolated because she was unable to bear her father Daksha's humiliation of her and her husband Shiva. The term sati was originally interpreted as 'chaste woman'. Sati appears in Hindi and Sanskrit texts, where it is synonymous with 'good wife'; the term suttee was commonly used by Anglo-Indian English writers. The word sati, therefore, originally referred to the woman, rather than the rite. Variants are:

The rite itself had technical names:

The Indian Commission of Sati (Prevention) Act, 1987 Part I, Section 2(c) defines sati as the act or rite itself.

The spelling suttee is a phonetic spelling using 19th-century English orthography. The satī transliteration uses the more modern ISO/IAST (International Alphabet of Sanskrit Transliteration), the academic standard for writing the Sanskrit language with the Latin alphabet system.

The origins and spread of the practice of sati are complex and much debated questions, without a general consensus. It has been speculated that rituals, such as widow sacrifice or widow burning, have prehistoric roots. The archaeologist Elena Efimovna Kuzmina has listed several parallels between the burial practices of the ancient Asiatic steppe Andronovo cultures (fl. 1800–1400 BCE) and the Vedic Age. She considers sati to be a largely symbolic double burial or a double cremation, a feature she argues is to be found in both cultures, with neither culture observing it strictly.