Is atheism just another religion?

No. Religions appeal to a supernatural realm controlled in most cases by a god or gods. Support for a religious idea can be in written form or orally passed down through the ages, supposedly proclaiming the wishes of a supreme being.

Atheists have no written revelations, no god or gods and do not accept the existence of a supernatural realm or a creative super-being as no evidence demands that they do. Atheism is therefore a rational evaluation of nature, whilst religions result from imaginative guessing.