One of the countless Parallel-Worlds that Superman has encountered in his adventures. On this parallel Earth, Superman is considered a fictional character but is still widely known through published adventures in comic books, movies, and other media.
External Links to Online Comics
"I Flew With Superman!" (SA No.9, 1983) 
"The Secret Message from Earth-Prime" (S No.400, Oct 1984) []
"The Last Earth-Prime Story" (SA No.411, Sep 1985)