Batman, I think.
Detective Comics. I believe it was issue number 27.
Although Spider-Man has been around a while, Batman was first. Spider-Man first appeared in Marvel comics in 1962. Batman first appeared in Detective Comics, later to become DC, in 1939.
Batman first appeared in Detective Comics 27 which has a cover date of May 1939. It was over a year after this that Captain America appeared in Captain America Comics 1, with a cover date of March 1941.
Superman first appeared in Action Comics #1, dated June 1938. Batman debuted in Detective Comics #27, the May 1939 issue, eleven months later. You didn't ask, but Robin first appeared in Detective Comics #38, dated April 1940 -- eleven months after Batman.
Superman's first appearance was in "Action Comics #1," cover dated June 1938. Batman's first appearance was in "Detective Comics #27," cover dated May 1939. Thus, in the real world, Superman is older. If, on the other hand, you are referring to characters, there is no clear answer to that which I am aware of. They are treated in the comics as contemporaries of similar age, and those ages aren't specified exactly. (Superhero ages rarely are these days, to better facilitate the "fluid" timelines that happen because the characters don't age nearly as rapidly as their readers.)
Detective Comics. I believe it was issue number 27.
May 1939, in Detective Comics #27
Batman's first appearance was in Detective Comics #27, printed in May of 1939.
The Spring issue of Batman came out in May 1940 ; this was the first issue in his own book .Batman's first appearance was in Detective Comics # 27 which came out in May of 1939 .
May 1939, in Detective Comics #27
Batman's first appearance was in Detective Comics #27, May of 1939. In 1940, he got his own series. He has appeared continuously in comics since then.
One but Batman made his first appearance in May 1939 in Detective Comics #27and Superman made his first appearance June 1938 in Action Comics #1 so really eleven
Although Spider-Man has been around a while, Batman was first. Spider-Man first appeared in Marvel comics in 1962. Batman first appeared in Detective Comics, later to become DC, in 1939.
Batman was first found in Detective Comics #27 (May 1939) .
Detective Comics no. 27, May of 1939.
Batman was first created by artist Bob Kane and writer Bill Finger in 1939, when the legendary superhero made his first appearance in the May issue of Detective Comics.
Detective Comics #27 first published in May 1939.