Fans worldwide are honoring Superman for Superman Day, an annual celebration of the iconic DC superhero. Created for DC Comics by writer Jerry Siegel and artist Joe Shuster, Superman's first appearance was in Action Comics #1. The comic book was published on April 18, 1938, which technically marks the "birthday" of the fictional character, though the issue was dated as June 1938 on the cover.

In 2013, DC Entertainment declared June 12 as "Man of Steel Day." At the time, the idea was to help promote that summer's release of Zack Snyder's Man of Steel which introduced Henry Cavill's incarnation of the character, but DC fans have been celebrating the superhero on that day ever since. In subsequent years, it has changed to become known simply as "Superman Day" to pay tribute to all of the various incarnations of the superhero.

RELATED: Michael B. Jordan's Val-Zod Superman Limited Series in Development at HBO Max?

As is the case each year, Superman Day is being observed by fans across the planet. One fan posted different incarnations of the Man of Steel and tweeted, "Happy #SupermanDay !! A character that has all the power in the world and he uses them to do good. A man who is dorky, wholesome but badass when he has to be. He will always rise to fight injustice, but even when he fails, he will never fail to be kind."

Recognizing the live-action Supermen, another fan posted images of Christopher Reeve, Brandon Routh, Henry Cavill, and Tyler Hoechlin, along with the message: "So streets are saying today is #SupermanDay Eyes Welp, time to remind y'all these are all equally great interpretations of the character Flexed biceps and hopefully some of them will interact soon enough Face savouring food Oh and #MakeManOfTomorrow !!!!"

Comics in the Golden Age used the occasion to pay tribute to another DC creator who further fleshed out the Superman universe, Otto Binder, with a post that reads: "Writer Otto Binder, who expanded the Superman universe much like he had done previously for Captain Marvel by cocreating Supergirl, Krypto, Brainiac, the Legion of Superheroes, & more."

Another Superman Day tweet reads: "One of the best comic book characters out there, Superman brings a message of hope and has inspired so many people at all ages. A character that remains and will probably always be relevant, to the comic book and movies's culture, also to all of us."

"I love Batman and Spider-Man, but the GOAT OF SUPERHERO GOATS is SUPERMAN #SupermanDay," says someone else.

And another fan posted, "Trunks or no trunks. President of a country or reporter in the big city. Bully turned hero or a small town origin. Whatever your preferred Superman, as long as you fight for truth, tolerance, and justice, then you're a valid Superman fan through-and-through. Happy #SupermanDay."

There's any number of ways for Superman fans to celebrate Superman Day. Beyond posting tribute messages on social media, fans could revisit some Superman material throughout its various mediums, like comic books, movies, and TV shows. Or, just take a moment to do something kind or helpful to someone else in the spirit of the Man of Steel. You can see plenty of other messages of fans paying tribute for Superman Day on Twitter.