Moni Nag (1925 – 7 December 2015) was an Indian anthropologist specialising in the politics of sexuality.

Born in India, Nag earned a master's degree in statistics from the University of Calcutta in 1946 and a PhD in anthropology from Yale University in 1961.^[1][2] He started his career in the Indian Statistical Institute^{[citation needed]} and worked on the Anthropological Survey of India before joining the Department of Anthropology at Columbia University in New York in 1966; he was a lecturer and later an adjunct professor and headed the social demography section in the International Institute for the Study of Human Reproduction.^[1][2] He was also a senior associate in the Population Council in New York^[3] and a patron and vice president of the Elmhirst Institute of Community Studies at Santiniketan,^[1] and served as chair of the population commission in the International Union of Anthropological and Ethnological Sciences.^[2]

Nag was a pioneer of demographic anthropology.^[3] He researched and published in the fields of human sexuality, fertility, family planning, HIV prevention, and sex work, with a focus on India, and both studied and worked for the rights of prostitutes in the Kolkata red-light district of Sonagachi;^[1][3][4][5] he was one of several academics working with the Durbar Mahila Samanwaya Committee there.^[6]

• Factors Affecting Human Fertility in Nonindustrial Societies: A Cross-Cultural Study (Yale University, 1962)^{[7][8][9][10]}
• Population and Social Organization (editor; Mouton, 1975)^[11][12][13]
• Sexual Behaviour and AIDS in India (Vikas, 1996)^[14][15]
• Sex Workers of India: Diversity in Practice of Prostitution and Ways of Life (Allied Publishers, 2006)^[16][17]