On Mars, J'onn J'onzz was regarded as the greatest warrior of the Green Martians. He started a family with his wife M'yri'ah after the birth of their daughter, K'hym. Tragedy struck when the White Martians incited a civil war and ravaged the Green Martian's city. As all his people were murdered, J'Onzz was accidentally teleported to Earth by Dr. Erdel.
In Middleton, Denver, Colorado, Dr. Saul Erdel attempted to send and receive a deep space signal to find alien life. Instead, he teleported a Martian to Earth. After forming a bond with Erdel, he learned much about his sense of heroism and good will. J'Onzz concluded that he wanted to be a force of good and protect his adopted home. He later became a superhero named Martian Manhunter and joined the Justice League.
Years later, he and the most of the Justice League agreed to help Alexander Luthor to defeat the Crime Syndicate. Martian Manhunter and the Flash disrupted one of Johnny Quick's smuggling operations. He appeared as a sea serpent and constricted Archer, one of Quick's Made Men, into submission then scuttled Quick's ship. The League's success caught the attention of President Wilson, who wanted to preserve status quo rather than challenge it. Manhunter read Wilson's daughter's mind without permission and presented the notion that the President was a soldier who didn't want to risk causing senseless bloodshed in a war, something J'onzz understood. Out of guilt and concern, J'onzz secretly followed Rose Wilson as she went to public rallies against the Syndicate. He saved her life from Archer and subdued him for the police, using his phasing powers to render the bowman's arrows useless, attacking him in the form of a monstrous alien animal and finally rendering the would-be assassin catatonic with a mental assault.
She implored Manhunter to use his true form around her and he in turn apologized for reading her mind earlier. In an unexpected turn, he realized they were attuned, their minds in sync to a strong degree. When Wilson tried to kiss him, J'onzz formed a mind-link with her and they both learned each others' pasts. President Wilson was displeased with the attempt on his daughter's life and authorized a strike on the Syndicate's lunar base. Manhunter accompanied them and reunited with the League. Despite the chance at love again, he upheld his promise to protect his universe's Earth and parted ways with Rose Wilson.
- Martian Physiology: The average Martian possesses the potential for the following power set:
- Shape-Shifting: Martians have psionic control of their physical for down to the molecular level. This allows them to a form of shape-shifting that allows them to mimic other forms, elongate aspects of their body, increase or decrease their physical size, and so on.
- Invisibility: Martians can cause the biopolymers in their bodies to lose their ability to reflect light, making the Martians invisible to normal light and human sight.
- Phasing: Martians can go through solid matter.
- Superhuman Durability
- Superhuman Strength
- Superhuman Stamina
- Extrasensory Input
- Super Hearing
- Martian Vision: Martian visual acuity greatly exceed human norms and allows for a wider range of information to be observed. This includes the following:
- Telepathy: Martians have the ability to read the minds of others and project their thoughts to varying degrees. They can also project their mental essences into a gestalt community known as the "Great Mind". Through this, the community can enhance the telepathic strength of other Martians. This power can also enable them to reverse the effects of amnesia or psychological brainwashing. 
- Astral Projection
- Mind Control: As an extension of this, Martians can also use the ability to alter a psychological profile of a target, enabling them to manipulate, and in some cases, outright control that individual. This practice is greatly discouraged however, and only rarely used. 
- Telepathic Relay
- Telepathic Assault
- Vulnerability to Fire: Martians are much more vulnerable to fire than the average Earth human. At times this has been portrayed as physical, psychological, or a combination of the two. The effect of this is to strip any Martian of their powers as they involuntarily lose control of their body.
- J'onn was voiced by Jonathan Adams
- Appearances of J'onn J'onzz (Crisis on Two Earths)
- Images featuring J'onn J'onzz (Crisis on Two Earths)
- Quotations by or about J'onn J'onzz (Crisis on Two Earths)
- Character Gallery: J'onn J'onzz (Crisis on Two Earths)
|Justice League member|
This character is or was a member of the Justice League of America, or the Justice League in any of its various incarnations, sworn by a duty to act as guardians of America and the world by using their skills and/or superpowers to protect Earth from both interstellar and domestic threats.