Michael is the main character throughout prison break.  Michael deliberately goes to jail because he believes his brother Lincoln is innocent.  Michael is going to try and break his brother out of jail and has planned the whole process very thoroughly. For example as you see in his photo his whole body is full of tattoos, every mark on his body is the blueprints of the entire prison. Michael is very smart but is  only motivated to help the people around him. 

Sarah Tancredi is the doctor at the prison. She is also the daughter of the governor. Throughout Michaels stay at Fox River (the prison) him and Sarah become good friends meeting everyday so Michael can get his medicine. When Michael ask is she can keep the infirmary unlocked so he can escape she listens t him and does it.  After they meet again once Michael is out of prison they start dating and fall in love. 

Fernando Sucre is Michaels cell mate when he goes to prison. Sucre and Michael become friends in prison and when its time to break out Michael takes Sucre with him. Throughout the entire show Sucre always has Michaels back when in trouble and they become very close friends throughout there journey. 

Brad Bellick is the main officer at the prison. He is a very shady cop making deals and trades with other inmates. Bellick does not like Michael and is always trying to get hime in trouble and hurt.  This will hurt Bellick in the future and will get him thrown in jail. Near the end of the show Brad apologizes to Michael and they are actually on the same team for a little while.  

Alexander Mahone was an agent working for the FBI to try and catch the Fox River eight who are all of the inmates including Michael who escaped from the prison. Even though he was a great agent and good at catching criminals he also has a dark side. Agent Mahone has done some bad things in the past and to forget about what he did he takes drugs. Also he works for this company in the government and they told him if he catches any prisoners don't bring them to jail just kill them.

Paul Kellerman is a secret agent, and is so secret in fact that he doesn't even exist on paper.  He is the person that helped frame Michael's brother Lincoln to be put in jail and be killed. He has been assigned a project to fake the death of the vice presidents brother  and choose Lincoln to frame as the killer. Later in the show however he leaves the company/government and fights against them to take them down.