Atheist Fundamentalism 

Atheist Fundamentalism is an oxymoron, because, fundamentalism implies a subscription to a belief set like a text book. One could be fundamental in a non-theistic philosophy, but, it is impossible to be an atheist fundamentalist.

However, in the context of it being used as an insult, it is used to denote atheists who are 100% certain that god does not exist (positive atheism) and hold anti-religious stances. This is the opposite of a religious fundamentalist who is 100% certain that god does exist and hold anti-atheist stances.

Atheist Fundamentalism is the polar opposite of religious fundamentalism because both regard their beliefs as being objectively correct while being just as intolerant as each other.

Atheist Fundamentalism by Kelmeer23 March 17, 2023

Atheist Fundamentalism

A rigid, literalist adherence to a particular strain of atheism—usually scientific materialism—that treats any departure from its dogmas as heresy. Atheist fundamentalism rejects not only belief in gods but also agnosticism, spiritual naturalism, and even moderate religious belief as "weakness" or "apologetics." It demands total ideological purity, often excommunicating fellow atheists who question materialism or show sympathy for religious people. It is fundamentalism without God, but with all the intolerance.

Example: "When she said she respected her grandmother's faith, the online atheist group called her a 'faith enabler.' Atheist fundamentalism: demanding purity of unbelief."

Atheist Fundamentalism by Dumu The Void April 18, 2026

Fundamentalist Atheist 

An atheist who displays all of the irritating behaviours of a Fundamentalist Christian.

They tell Christians what they are "supposed" to believe in order to be Christian.
They judge everyone with differing beliefs as being inferior or less intelligent.
They try to convert others to their way of thinking.

They show complete disrespect and even insult those with differing beliefs, without provocation.

Bob is such a Fundamentalist Atheist. I told him I'm a Christian but I don't believe in hell and he started telling me how I'm not really a Christian. What a dick.

Fundamentalist Atheist by Mongo1313 June 8, 2014