Is Atheism a Religion?
Many theists make the claim that "atheism is a religious belief". Is that claim reasonable?
Atheism has no organization, no creed, no rules, no guideline, and no guiding authority. To be a religion it would need to have some organization beyond simply rejecting a belief in god.
Atheists, like all humans, have various beliefs, but individually holding a belief does not make a religion.
Two Main Types of Atheism
Gnostic is the actual belief that no gods exist. I am on the fence as to whether this counts as a religion or not. It is a belief about god something like a religious belief; it is a positive statement about the universe and could be used as a guiding principle. Yet as a religion, it is completely different from any other religion because all religions involve a god of some type. About 50% of atheists fall in this category.
Agnostic is simply the rejection of existing religions. There is no belief per se. This person is saying “I don’t know what the truth is, but I am convinced that that, that, and that are false.” This is a position of critique of existing religions, would proffering any beliefs of their own. This is certainly NOT a religion. The other 50% of atheists fall in this category.
See: https://meta.purplehillsbooks.com/2020/05/14/what-does-atheism-mean/
Beliefs are not Organized
Christians will often claim that atheists hold certain beliefs about the world. All humans have beliefs about the world, that is how the mind works. We call the beliefs knowledge when they are credible enough. All human action is based on these things you have learned, whether they are true or not.
They will claim that belief in evolution constitutes a belief similar to belief in creationism. This is a false equivalence since evolution is backed by museums full of evidence which the clever apologist dismisses with persuasive lies. Still, not all atheists accept evolution. There is no rule or guideline that in order to be an atheist you must believe in evolution. A religion is an organization that promotes particular ideas simply as part of being that identity, but there is no such organization for promoting particular ideas for this purple.
Not all atheists are scientists either, although in the US a scientific world view is often adopted by atheists. There is no rule whereby one atheist could claim that another is not an atheist because they don't have a scientific worldview. There is simply no requirements on being an atheist, and atheists are free to believe many many crazy things.
Even if a lot of atheists believe the same thing, such as the sky being blue, or the earth going around the sun, that does not make a religion. There is only one thing in common with all atheists, and that that they don't believe in a God. That is a description, and it does not define what one must believe instead.
An Alternative to Religion
When one makes a list of religious affiliation, one needs a category for non-religious. Same as when talking about hairstyles, you need a category for bald. When talking about cuisines, you need a category for fasting. You need a category for the negation, and atheism is often used as the stand-in for this.
This is not actually appropriate. There are religions that don't believe in a god, and so they are actually atheist. There are also atheist who believe in a mystical supernatural existence, such as ESP, panpsychism, or paganism, which might have a collective higher power, but still are not considered as believers in a traditional god. One needs to distinguish carefully between atheist and simply non religious.
The alternative to religions should be "non-religious" and not "atheist".
Conclusion
Atheism does not qualify as a religion, but I don’t push back on people who insist that it is. It doesn’t really matter, and it depends on what specifically you mean by religion. If they want to say it is a religion, it is not worth fighting over.
