Johanna Reyes is the former representative/speaker of Amity and was the leader of the Allegiant group. She transferred from Candor. She left Amity to go with Marcus Eaton group, and later start the Allegiant group.
Johanna most notable feature is a long scar running from her left to her right cheek. It is said briefly in Allegiant that Tobias Eaton believes that she got the scar from being attacked by either her parents or a friend.
It is later revealed by Veronica Roth that Johanna received the scar when a factionless man scratched her face with a knife during an abusive feud. It is believed that she got it when she was in Candor.
Although the Amity do not have an official appointed leader as they all decide together, Johanna serves as their speaker. It is revealed later that although she may disagree with some of the final decisions of the Amity, she doesn't do anything about it because of their Amity morals, saying that she keeps her disagreeing thoughts to herself.
It is also shown during her conversation with Tobias that, like Christina who also grew up a Candor, she still has her Candor-trained senses. She also tells Tobias that if they do not wish to be affected by the peace serum, they should avoid the Amity bread.
Before Marcus, Tris Prior and Christina go to the Erudite compound, they return to the Amity compound to ask for the help of the Amity, the escaped Erudite, and the remaining Abnegation who stayed there.
Johanna calls for a meeting where she asks the Amity that they reconsider their previous decision to remain uninvolved to protect the innocent Erudite members, saying that the knowledge they have worked for so long is necessary for their survival. She proposes that they join as peacekeepers. This causes arguments among the Amity instead of the normal discussion among the members.
When the final decision was still to uphold their previous decision, she speaks further, saying that although she does not wish her faction to be divided, her conscience is against the final decision, saying that she will go into the city with Marcus' group and anyone who feels the same way should come with them. She adds that if the faction sees this as defection, she will understand and will leave Amity with love. A few of the Amity later join her.
After the attack, when the Dauntless and Factionless have all gathered the others into the lobby, Johanna appears and speaks curtly with Tori before Tori sends her back to the Amity for a message, apparently excluding them from the new political system. Before she leaves, she hints at the factionless' current state of power over them.
She seems to like Marcus, after Tris watches them walking in the Amity greenhouse and later sees her kiss him on the cheek. And apparently at the beginning, she had a dislike for Tris and Four, particularly because of their Dauntless status.
In Allegiant, Johanna is the leader of the Allegiants, a rebel group along with Cara. The Allegiants fought for the factions to be restored. Later on in the book, she is seen holding a gun while raiding a storehouse, which had never been done by the Amity. She also recruits Marcus into the Allegiant (though she tells him they are no longer friends). In the end, when Evelyn Johnson came to negotiate a treaty, Johanna reminds Marcus that she is the leader of the Allegiant and accepts Evelyn's offer as Marcus was about to decline it.
In the sequel, Insurgent, Johanna is played by Academy Award Winner Octavia Spencer.
When Tris arrived at Amity, Johanna allows her to stay with them, and when Tris causes trouble, Johanna allows her to stay again. She tells her this is her last chance. When Tris runs out, Johanna is shocked. As the film ends and the Amity faction run to the wall in order to explore the outer world, she smiles in the sun from the window of the Amity house.