Jimmy "B-Rabbit" Smith is the main protagonist and a young underground rapper who frequently performed in rap battles, well known for beating the rapper Papa Doc and becoming the new champion.
Nothing is known of his father and it is only slightly clear about what he was doing before the events of 8 Mile, according to future he's a "lyrical genious" and would probably have been recording and writing songs many years before as well. At the beginning of 8 mile, we see him preparing for a rap battle at the shelter (an underground club), upon entering the shelter and preparing for battle he takes the stage to face Lil' Tic (Proof), much to his embarassment he chokes and leaves the venue in disgrace.
The rest of the film focuses on his life and deciding about how he wants to make it in the rap game, after losing his job at a Pizza parlour and splitting up with his girlfriend Janine, he's forced to move back in with his mother who lives at a trailer park, at first there is a heating conflict with his mother's boyfriend Greg who was at one time a school mate of Rabbit's. He at some point started working at a pressing plant in Detroit in order to earn some money, but it was not enough for him to sustain himself properly, he was also scolded constantly at work by his boss for being late.
When he isn't working, he's seen hanging out with his friends Future (the rap battle host), Sol, DJ Iz and Cheddar Bob who are in their own way social outcasts and dream about finding their way out of the ghetto and living a life of luxury. His other friend Wink see's that B-Rabbit is a talented lyricist and rapper and has connections with WJLB a radio station that has access to studios and promotes the work of other artists, Wink is also an associate of the 'Free World Leaderz' a gang that serves as the primary antagonists of Jimmy and the rest of the 313 crew.
While working one day he sees a blonde girl by the name of Alex Laterno whose looking for her brother, immediately there is a flare between them and they don't meet until later on at a parking lot gathering, sometime later at the abandoned house party she reveals that she is an aspiring model with the intention of getting hooked up and going to New York. They start a brief relationship which essentially ends when he catches Wink and Alex having sex in one of the studios, a fight breaks out and Jimmy leaves. That night Jimmy comes to collect his sister Lilly who was at a neighbors because their mother was intoxicated after Greg had left her following her impending eviction, he's confronted by Wink who has completely aligned himself with Papa Doc's gang and they proceed to attack him.
By the end of the movie, Future signed Jimmy up for another battle much to his dismay at first, but decides that this is the best way to gain confidence and the respect of everyone in the battling community, he takes on two members of Popa Doc's gang in a battle (Lykety Split and Lotto) of whom he easily defeats with clever comebacks that are progressively impressive each time. Popa Doc being the defending "champion" allows B-Rabbit to battle first, B-Rabbit starts the battle mocking the free world leaders before ackowladging any flaws that Popa Doc might have as ammunation against him, (He lives with his mother in a trailer, he's "white trash", Chedder Bob shot himself). In a smart twist, he uses these as a springboard to reveal to everyone secrets about Popa Doc, for example Popa Doc wasn't a real thug but instead lead a privilaged background complete with private schooling and a stable family environment. Humilated and unable to make a comeback, Popa Doc leaves with the rest of the Free World gang. Jimmy decides to return to work instead of celebrating his battle victory and reveals to his friends that he plans to "make it on his own". He then leaves and it is implied that he would become what Eminem is now.
Jeneane (last name unknown): Jimmy had a relationship with Jeneane. Jeneane thought they were going to split up, so she told Jimmy that she was pregnant. Jimmy does break up with her, but he says that it's not her, instead it's him. He left his car with her because he thought she was pregnant.She later comes to his job and asks him why he hasn't called.While talking to him it is revealed that B-Rabbit never actually broke up with her and that he just left without saying a word. Then B-Rabbit says to go home. Then she starts to make fun of him and she goes home.
Alex Latorno: She is the brief love interest of Jimmy during the film, the relationship disintergrates when she has sex with Wink and wishes him luck before his final rap battle.
Stephanie Smith: His relationship with his mother has been one of emotional turmoil, she's a pathetic alcoholic who dated bad men, has no job, scrounges on welfare and is about to be evicted from their trailer. She somewhat feels guilty about about the life she's given Jimmy and Lilly but can never really seem to get motivated enough to be able to turn it around. Things are at their worst between the two when they argue over Greg Buehl, an idiot redneck and former classmate of Jimmy's who is currently involved in a relationship with Stephanie, she blames him for Greg abandoning her and seems to act like their current situation isn't really her fault. By the end of the film it is revealed that she went to bingo and won $3200 which was more than enough for her to pay the overdue rent and avoid losing her home, she somewhat seems keen to change her life for the better.
Greg Buehl: Jimmy first encounters Greg having sexual intercourse with his mother upon returning to the home, they instantly start to fued after Greg taunts Jimmy about his job at the pressing plant, later on when Greg finds out about Stephanie's eviction he begins to get rough with her, Jimmy intervines and fights Greg causing him to leave and he is never seen again in the film.