I am writing a novel. Can I mention fictional heroes like Batman and Superman in my novel as existing works of fiction or would this go against copyright laws?

Common confusion. Mentioning Superman and Batman would not go against copyright laws, because you can’t copyright a name.

The thing you need to be worried about is trademark law.

Copyright and trademark are completely different things. Batman and Superman are trademarks.

So. The question is not would it violate copyright laws, but would it violate trademark laws.

And the answer is “no, but.”

No, just mentioning trademarks in a work of fiction does not violate trademark laws. You can’t copyright have a character who drinks Stash® tea, drives a Toyota® Corolla®, loves listening to Green Day®, has a Neuralink® implant, and watched all the John Wick® movies on her American Airlines® flight to Harrods® in London.

All of that is okay.

What you cannot do is:

Imply any endorsement or association between your work of fiction and those trademarks;

Set your work of fiction in the same universe as a trademarked or copyrighted world or character (for example, it is okay to say that your character loves the Batman comics, but it is not okay to say Batman taught your character to fight crime, because that puts your work in the Batman universe, and Warner Bros will strike down with great vengeance and furious anger);

Use other people’s trademarks to promote, market, or advertise your work (no putting the Superman logo on your novel’s cover!);

Cast aspersions on the trademark owners or their products or otherwise use or reference the trademarks in a disparaging or derogatory way (no suggesting that Toyota Corollas burst into flames without provocation, or that the artist who created Superman was a kiddie-diddler); or

Tie your work into the trademarked properties or characters without permission.

So yes, a character can say “my favorite movie is the Batman with Heath Ledger in it,” no you cannot have your character say “Batman gave me this utility belt,” and no you cannot put the Batman® logo on your cover.