Christian extremism is a term that encompasses a wide range of Christian-based beliefs considered to be fundamentalist and violent in nature. The term is not as widely used as Islamic extremism. In general colloquial speech it is used pejoratively as an umbrella term to cover Fundamentalist Christianity, including political ideologies such as Christian Reconstructionism.

However, the line between Christian Fundamentalism and Christian Extremism is blurred. One school of thought places Christian movements that resort to violent tactics under the label of terrorists. The bombing of abortion clinics and killing of doctors involved in abortions is a notable example of Christian terrorism. Those that involve themselves in political campaigns to, for example, remove the separation of church and state in countries like the United States, outlaw abortion, sex before marriage, gay marriage or reduce gay rights, are often more widely considered fundamentalists.

The events surrounding the terror attack in the United States of 2001 forced a very black and white view of the difference between religious extremists and moderates - extremists were no longer defined as those simply carrying out violent acts in the name of their religion, rather also defined as those inciting other members of their religion to hatred of other beliefs. Randall Terry, founder of pro-life organization Operation Rescue, said the following at a pro-life rally in 1993:

"I want you to just let a wave of intolerance wash over you. I want you to let a wave of hatred wash over you. Yes, hate is good... Our goal is a Christian nation. We have a biblical duty, we are called on by God to conquer this country. We don't want equal time. We don't want pluralism."

Applying the same principles, this would make Randall Terry, by definition, an extremist. However, his views are shared by many prominent Christian ministers and televangelists such as Jerry Falwell and Pat Robertson. People such as these however, whose views and methods of expression may nonetheless be considered distasteful by non-Christians and even many moderate Christians, have never directly incited violence against members of organizations, groups or religions deemed contrary to Christianity.

In 2002, Saudi Arabian media used the term "Christian extremist" as a retort against the colloquial use of "Islamic extremist", to refer to the Christian fundamentalist influences that were acting on United States government policy.