[Librarian]

Depends what you mean.

If you mean the first heroes in tights, masked vigilantes, or heroes with abilities above those of normal men.

Because they all vary. Characters with non-human abilities are as old as time, dating back to some of the earliest myths and legends and folk stories, every culture has them with various folk heroes and other myths that stretch to even the modern variations of occult urban myths.

If you mean masked vigilantes, they go back pretty far too. In literature at least you have a wide range of various types and what inspired them. From the Scarlet Pimpernel to Zorro and where his origins came from in a folk anti-hero, and many other variations of that as well scattered through out old literature. Pulp fiction heroes were a kind of literature staple through some centuries and are what gave rise to later heroes like Batman and similar.

If you mean heroes in tights of the comic world, then you're talking roughly the 20s and 30s in the US. With some of the earliest comic book heroes like the Phantom, and similar.

In Japan it traces back in media from to roughly the 60s. Astroboy, and later Cyborg 009 which is considered the first "superhero" team there. Where they transitioned from characters of legend and folk heroes to the actual trope of superheroes.

So it really depends on how define "Superhero". And even the genre itself evolved from other pulp fiction origins, which those themselves evolved from various folk heroes and concerns of the time. Like how even Ultraman evolved from Japanese fears of occupation because of American Military bases, which carried over to his overtones of an extra terrestrial authority figure that was keeping the monsters at bay, with questions of "friend or foe" etc. Same as how Godzilla evolved from the fear and grief of Atom Bombs.

Nothing is born in a vacuum.