ReiBert

ReiBert is the slash ship between Reiner Braun and Bertoldt Hoover from the Attack on Titan fandom.

Canon
Throughout their childhood in Marley, Bertholdt and Reiner trained together to become Marleyan warriors; they became quick friends due to Reiner's meek personality and Bertholdt's friendliness. They befriended Marcel and Annie Leonhart whom they were later assigned a mission with to destroy the Subjects of Ymir living within the walls and recapture the Founding Titan. Reiner and Bertholdt share two common goals: To return home and to bring glory to the shunned Eldians back in Marley.

The two are almost always seen together, they were introduced together among the 104th Training Corps and as partners. After breaching a hole in Wall Maria together as the Colossus and Armored Titans, the guilt Reiner carried started affecting his grasp on reality, putting stress on their relationship. Reiner developed a dissociative-identity disorder(split-personality), where his "Soldier" personality started taking over his "Warrior" one.

Despite Reiner's mental instability, Bertholdt continues to trust his judgement and follow him. They show great concern for each other such as the time Bertholdt saved Reiner from a titan at Utgard Castle and aiding him in kidnapping Eren.

When Reiner is defeated by the Scouts and is left almost dead, Bertholdt changes the original plan Zeke made and instead of bombing Shiganshina District as originally planned, he chooses to save Reiner instead. This decision eventually had a fatal consequence for Bertholdt, who, because he failed to kill the Scouts in the beginning, ended up dying. His decision to put Reiner's survival above Zeke cost Bertholdt's his life and the mission's success.

Fanon
In episode 29, Ymir and Reiner's conversation may imply that Reiner is gay/bisexual. As Ymir says to Reiner that he "didn't look like the type who would be interested in girls." This has caused a huge debate in the fandom whether Reiner is gay or not, and that if his relationship with Bertholdt may actually be deeper than just friends.

They're the most written ship for both characters on AO3.

Fandom
FAN FICTION

TUMBLR

Trivia

 * Reiner and Bertoldt share a character theme song, "Alternative Drive." It is sung by Bertoldt's voice actor, Tomahisa Hashizume and Reiner's, Yoshimasa Hosoya.