Christian Fundamentalism refers to the movement that arose mainly within American and British Protestantism in the late 19th and early 20th centuries, led by conservative evangelical Christians in reaction to modernism and liberalism in the mainline denominations. This movement included not only denominational evangelicals (such as the Princeton theologians B. B. Warfield and J. Gresham Machen), but a growing breed of premillennial and dispensational independants such as D. L. Moody, R. A. Torrey, and the independant Bible college and Bible church movement.
Taking its name from The Fundamentals (1910-1915), a twelve-volume set of essays designed to combat Liberal theology, the movement grew by leaps and bounds after World War I. The term "Fundamentalist" was perhaps first used by Curtis Lee Laws, a British journalist for the Watchman-Examiner, in 1920 to designate those who were willing to do "battle royal for the Fundamentals." 
Fundamentalism versus broader Evangelicalism
The nature of the Fundamentalist movement, while originally a united effort within conservative evangelicalism, evolved during the early-to-mid 1900s to become more separatist in nature and more characteristically dispensational in its theology. Premillennialism, dispensationalism, and separatism began to overwhelmingly characterize the most popular leaders, which also had an effect on the way that "evangelicals" as a whole were perceived by outside observers. This eventually led to purposeful distinctions between fundamentalism and what was seen as the broader evangelicalism.
For example, it should be noted that The "Princeton Theologians", particularly Machen, eventually distanced himself from the fundamentalist movement because of its emphasis on separating from culture instead of engaging it. In a letter to the board of trustees of Bryan Memorial University refusing their offer to make him president Machen wrote:
I never call myself a "Fundamentalist." There is indeed, no inherent objection to the term; and if the disjunction is between "Fundamentalism" and "Modernism," then I am willing to call myself a Fundamentalist of the most pronounced type. But after all, what I prefer to call myself is not a "Fundamentalist" but a "Calvinist"—that is, an adherent of the Reformed Faith. As such I regard myself as standing in the great central current of the Church's life—the current which flows down from the Word of God through Augustine and Calvin, and which has found noteworthy expression in America in the great tradition represented by Charles Hodge and Benjamin Breckinridge Warfield and the other representatives of the "Princeton School."^^
- ? D. G. Hart and John Muether, A Brief History of the Orthodox Presbyterian Church ISBN 0-934688-81-8.
- R. A. Torrey, ed. The Fundamentals, 2 vols. Baker, 2003. (reprint)
- Malise Ruthven, Fundamentalism: A Very Short Introduction. Oxford, 2007.
- George M. Marsden, Understanding Fundamentalism and Evangelicalism. Eerdmans, 1991.
- __, Fundamentalism and American Culture. Oxford, 2006.
- Hart, D. G., and John Muether. Fighting the Good Fight of Faith: A Brief History of the Orthodox Presbyterian Church. Philadelphia: The Committee on Christian Education and the Committee for the Historian of the Orthodox Presbyterian Church, 1995. ISBN 0-934688-81-8