Is atheism a religion? No, not truly a religion, as I define religion to be “man’s search for God.” Since atheists do not believe in a God then they are not searching for one.
However, if the question was “is atheism a faith tradition” then I might answer yes. Atheists have faith, just not in a deity. Atheists are living out their lives like everyone else, trying to find some understanding of the big “why” questions, but do not find their answer in a supreme being, but in trying to find the answers, they are putting their faith or trust in something. At least, that is my current understanding of atheism, and of course, it will look different from each atheists perspective.