Nancy Tatom Ammerman (born 1950) is a professor of sociology of religion, now at Boston University, who wrote a controversial report about the Branch Davidians and Waco.

In 1984, Ammerman joined the faculty of Emory University. Her book, Baptist Battles, won the 1992 Distinguished Book Award from the Society for the Scientific Study of Religion.

She was one of a panel of academics commissioned in 1993 by the U.S. government to analyze what went wrong in its dealings with the Branch Davidians at Waco.

Ammerman's report concludes that neither the ATF nor the FBI took David Koresh seriously as a religious man, but rather adopted the "anti-cult" point of view of deprogrammer Rick Ross. She wrote: Ammerman disputes the view that Koresh's followers were "hostages", noting that some of them left their Mount Carmel Center between the initial ATF raid and the last day of the standoff.

She also criticizes the Justice Department for ignoring the recommendations of FBI agents who suggested taking Koresh's religious faith as (at least possibly) sincere and backing off instead of applying ever-increasing pressure.

She also wrote: Ammerman herself has been criticized by some within the anti-cult movement as a "cult apologist." She is on the referral list of the Scientology-run Cult Awareness Network.

For much of the last decade, Ammerman's work has focused on American congregations. Her most recent book, Pillars of Faith: American Congregations and their Partners (University of California Press, 2005), describes the common patterns that shape the work of American's diverse communities of faith. Her 1997 book, Congregation and Community, tells the stories of twenty-three congregations that encountered various forms of neighborhood change in communities around the country. Along with a team of others, she edited and contributed to Studying Congregations: A New Handbook.

In 1995, Ammerman left Emory University to teach at Hartford Seminary. Since 2003, she has been at Boston University.

Her books include:

- Ammerman, Nancy T (Ed.). Everyday Religion: Observing Modern Religious Lives. (New York: Oxford University Press, 2006).

- Ammerman, Nancy Tatom. Pillars of Faith: American Congregations and their Partners ( University of California Press, 2005). WINNER, 2005 Distinguished Book Award, Sociology of Religion section, American Sociological Association.

- Dudley, Carl S., and Nancy T. Ammerman. Congregations in Transition. (San Francisco: Jossey Bass, 2002).

- Ammerman, Nancy T., Jackson Carroll, Carl S. Dudley, and William McKinney (eds.). Studying Congregations: A New Handbook. (Nashville: Abingdon, 1998).

- Ammerman, Nancy Tatom. Congregation and Community. (New Brunswick: Rutgers University Press, 1997).

- Ammerman, Nancy T. and Wade Clark Roof (eds.). Work, Family, and Religion in Contemporary Society. (New York: Routledge, 1995).

- Ammerman, Nancy T. (ed.) Accounting for Christian Fundamentalisms. in Accounting for Fundamentalisms, Martin E. Marty and R. Scott Appleby (eds.). (Chicago: University of Chicago Press, 1994).

- Ammerman, Nancy T. (ed.). Southern Baptists Observed: Multiple Perspectives on a Changing Denomination. (Knoxville: University of Tennessee Press, 1993).

- Ammerman, Nancy Tatom. Baptist Battles: Social Change and Religious Conflict in the Southern Baptist Convention. (New Brunswick, NJ: Rutgers University Press, 1990). WINNER, 1992 Distinguished Book Award, Society for the Scientific Study of Religion. Portions reprinted in Sociology: The Central Questions, 2nd ed., by William Kornblum (Harcourt, 2001).

- Ammerman, Nancy Tatom. Bible Believers: Fundamentalists in the Modern World. (New Brunswick, NJ: Rutgers University Press, 1987). Portions reprinted in Religion North American Style, ed. by Thomas E. Dowdy (Rutgers University Press, 1996); and The Practical Skeptic: Readings in Sociology, by Lisa J. McIntyre (Mayfield, 2001).