| Issue | #300 |
| Published | September 1962 |
| Cover Price | 0.12 |
| Pages | 36 |
| Editing | Mort Weisinger |
| Notes | Legion begins continuous run through issue 380; Legion next appears in Superboy 100 and Superman 156. |
| Characters | Legion of Super-Heroes [Superboy; Sun Boy; Saturn Girl; Cosmic Boy; Lightning Lad, Triplicate Girl; Mon-El] |
| Genre | superhero |
| Pencils | Curt Swan |
| Inks | George Klein |
| Letters | Ira Schnapp |
| Notes | Legion begins continuous run through issue 380; Legion next appears in Superboy 100 and Superman 156. |
| Reprinted | in DC Special Blue Ribbon Digest (DC, 1980 series) #1; in Legion of Super-Heroes Archives (DC, 1991 series) #1 |
| Characters | Superboy; Lana Lang |
| Synopsis | Lana and Clark are accidentally transported to a strange world where Clark must make her think they both have superpowers in order to prevent her from guessing he's Superboy |
| Genre | superhero |
| Script | ?; Mort Weisinger |
| Pencils | George Papp |
| Inks | George Papp |
| Letters | Joe Letterese |
| Editing | Mort Weisinger |
| Characters | Varsity Vic |
| Synopsis | Vic asks Melissa to marry him so he can feel what it's like to lose a million dollars. |
| Genre | gag |
| Script | Henry Boltinoff |
| Pencils | Henry Boltinoff |
| Inks | Henry Boltinoff |
| Letters | Henry Boltinoff |
| Characters | Little Pete |
| Synopsis | Pete loses his ice cream to Willie's dog. |
| Genre | gag |
| Script | Henry Boltinoff |
| Pencils | Henry Boltinoff |
| Inks | Henry Boltinoff |
| Letters | Henry Boltinoff |
| Characters | Legion of Super-Heroes [Cosmic Boy; Saturn Girl; Lightning Lad; Sun Boy; Superboy; Chameleon Boy (statue); Bouncing Boy (statue); Shrinking Violet (statue); Invisible Kid [Lyle Norg] (statue)]; Lex Luthor; Urthlo; Mon-El |
| Synopsis | At a regular meeting of the Legion of Super-Heroes, the Legionnaires lose control of their powers. Urthlo arrives and announces that he now controls the Legionnaires' powers and there is nothing they can do about it. But Saturn Girl comes up with a serum to temporarily cure Mon-El and immunize him against lead, and Superboy releases him from the Phantom Zone to knock out Urthlo, who turns out to be an automaton created by Lex Luthor sent into the future to destroy the Legion. |
| Genre | superhero |
| Script | Jerry Siegel |
| Pencils | John Forte; Al Plastino (page 4 and some Superboy and Luthor heads only) |
| Inks | John Forte; Al Plastino |
| Letters | Milton Snapinn |
| Editing | Mort Weisinger |
| Notes | Beginning of first regular Legion series. Mon-El becomes a member of the Legion in this story. |
| Reprinted | in Action Comics (DC, 1938 series) #377; in Adventure Comics (DC, 1938 series) #497; in Legion of Super-Heroes Archives, The (DC, 1991 series) #1; in Superman: Tales from the Phantom Zone (DC, 2009 series) #[nn] |
| Characters | Jerry the Jitterbug |
| Synopsis | Jerry takes Jane for dinner, but it's a cheap place. |
| Genre | gag |
| Script | Henry Boltinoff |
| Pencils | Henry Boltinoff |
| Inks | Henry Boltinoff |
| Letters | Henry Boltinoff |