Thelma Dickinson
Louse's best friend is a naive housewife who is treated without any respect at all by her brash and bullying husband Darryl, a car salesman. She does not like her life very much and is exictied for her road trip because it will be a change from the grind and monotony of her everyday life. Thelma is not very world wise and believes that Harlen is going to be a nice guy who is fun to dance with; she does not realize that he is going to try to rape her.
Thelma does not understand Louise's reluctance to go to the authorities because from her perspective the shooting was to protect and defend her, and to prevent Harlan from raping her.
Because she falls wildly and head-over-heals for J.D., Thelma does not have her guard up as much as she should. Even after she finds out that he is a thief she leaves him alone int heir hotel room with Louise's life savings, which of course he steals. This leads to her holding up a convenience store at gunpoint to try to reimburse Louise. Thelma spends much of the trip feeling guilty - for losing the money, for picking up J.D. in the first place and for putting Louise in the position of having to flee the authorities. She is aware hat Louise's relationship with Jimmy is a good, positive one and the complete opposite of her marriage. For this reason she tells Louise that she does not have to flee with her. It is Thelma's idea for the women to commit suicide rather than surrender to authorities and spend the rest of their lives in jail.
Louise Sawyer
Feisty Louise is a tell-it-like-it-is kind of woman who is definitely the stronger of the two women. She has been through trauma in her life - she was raped whilst she was in Texas and consequently is convinced that nobody will believe that either Thelma said "no' to Harlan or that the shooting was in defense of her friend. Louise is in a good relationship with Jimmy, a man whom she loves, and who loves her, but who is never around because of his career.
Louise is the clearer-thinking of the two women. She is also the victim of their friendship in a way as her life savings are stolen by J.D. after Thelma brings him along with them. Ultimately Louise is too loyal to Thelma to leave her to flee alone.
J.D,
Felon and thief J.D. hitches a ride with Thelma and Louise after jumping parole. Of course, he does not share this with them right away, but Thelma does learn about his history after taking him back to her hotel room and spending the night with him. He is also happy to share his knowledge of being a thief with her. J.D. is not a dangerous man but an habitual petty criminal who cannot seem to help himself when it comes to stealing from others.
Jimmy
Louise's boyfriend is a musician and because of this is not home very much; he loves Louise, and proposes to her when he brings her the money she requested, which is actually very romantic in many ways. He proposes to her but is turned down.
Darryl Dickinson
Used car salesman Darryl is a bully and extremely disrespectful to Thelma. He is scathing and talks down to her and she is consequently quite afraid of him.
Hal Slocumb
Slocumb is a sympathetic figure who seems to genuinely feel sad for the women and he predicament they now find themselves in. A detective who believes a woman when she tells him she has been raped, he is immediately understanding about the women's reluctance to report Harlan's attempted rape, because he knows that when Louise reported her rape years earlier she was not believed or taken seriously. He believes that Harlan tried to rape Thelma and also believe that the shooting was not really a murder. He wants the women to surrender so that they will be taken alive. He tries until the end to persuade them to surrender.
Harlan
Although seemingly peripheral, Harlan is in fact the most important character in the film because he is the catalyst for the tragic chain of events that unfold in it. It is pretty clear that he goes to drink at the roadhouse bar regularly and it is likely that the attempted rape is something he has attempted before. He has no respect for women and has clearly attempted raping them with this method before.