Atheists don't have no songs

I love Steve Martin.

God Was Never On Your Side by Motörhead. Lemmy was always highly critical of religion, and I think that is his definitive statement on the matter. He's an underappreciated writer.

Maybe "Dear God," by XTC?

I enjoy Tim Minchin's fun piano playing and cheeky lyrics: Tim Minchin - Thank You God

“Judith” by A Perfect Circle, and Tool’s “Wings for Marie” are both pretty down on religion. Both are excellent songs, and they are about the same person.

I don't think I know any, unless maybe A Perfect Circle's Judith counts. It's definitely anti-god.

Or possibly Thoughts of a Dying Atheist by Muse.

Two of my favorites are kind of tangential; but certainly involving atheism as a main theme:

Vampire Weekend "Unbelievers": https://www.youtube.com/watch?v=aJd5EMB9im0

Death Cab For Cutie "I Will Follow You Into the Dark": https://www.youtube.com/watch?v=3iV_1ESMHaI

All these comments and nobody's basic-bitch enough to mention Imagine by John Lennon? I don't know if it's the best song, but it's the obvious first one I thought of when I read the question.

Thank You God by Tim Minchin

https://youtu.be/IZeWPScnolo.

origin of species by mc frontalot

Pantera has a couple of nice ones. More about anti religion than atheism per se, but still.

Heresy: https://youtu.be/rc-19z52Da0

Slaughtered: https://youtu.be/8DnUwNops-E

I... don't really have a favorite song about atheism.

I'll just go with "I'm Free... Free Balling" by that guy who apparently really likes going commando. (I'll take misheard lyrics for 100, alex.)

“No Gods & Precious Few Heroes” by Dick Gaughan. A lot of his stuff is similarly themed: “Revolution” and “Stand Up for Judas” also come to mind. He’s a Scottish communist folk singer.

Bad Religion have a few, but that's pert'near cheating.

Holy Smokes by Aesop Rock.

Modest Mouse Third Planet.

It's very subtle, but there's a lot of atheist sentiment in there.

"The green and grey"

I don't know many, so I would go with The preacher and the slave. It's an old but good piece on the intersection of religion and capitalist oppression.

https://youtube.com/watch?v=Aqw0jROxPxs curious if this counts. (Relatable to me as an agnostic).

Probspot - God Shaped Hole

Would you say The Trees, also by Rush, is more about politics or religion? I take the line about “hammer, axe, and saw” to be about anything that divides people. Though it might not actually be about religion. I don’t know. I do like that song by them though.

"No" by the Subhumans, if you like old '80s punk. Anti-religion and anti-establishment.

https://www.youtube.com/watch?v=xmwAD7nHqaY

Lol nobody's mentioned Ghost yet? I'll go with watcher in the sky by Ghost.

I don't think it's my favourite, but a bit ago Tidal played "Mein Gott hat den Längsten" from Alligatoah for me. A rap song basically how his God has the biggest ... He reads between the lines of scripture and signals for his God with a pile of dead people. And all the plundering and murdering shows salvation to people and makes them blessed.
Not exactly atheism, more anti-religion. Songs has a lot of text and proceeds from Islam over Christianity to death cults.

Man in the Box by Alice in Chains

Big Houses by Squalloscope is a song about leaving formal religion while having appreciation for the human aspects that modern religion is distinct from. My favourite line is "I have a soft spot for your ancient book of horror stories."