Who is the main character in Jerry Spinelli's Stargirl?

The main character is Leo Borlock who narrates the story, even though he focuses mostly on how he and his high school get to know Stargirl, how they treat her, and how his relationship with her develops. The conflict for Stargirl is person vs. person and person vs. society; but mostly, it's Leo vs. himself. Both Stargirl and Leo struggle to find themselves within their community and at MAHS--Mica Area High School. They discover what each other is willing to sacrifice in order to make their relationship work. For example, Leo is willing to date Stargirl even if she is the most unpopular girl at school. Then she shows her devotion to their relationship by dropping the name "Stargirl" and going back to her real name--Susan Caraway. She goes back to using it so Leo won't be ostracized for dating her as "Stargirl." As a result, Stargirl loses herself in the role as Susan. She becomes unhappy and realizes that giving up on who she is in order to make a boyfriend happy isn't worth it. Then, out of embarrassment for dating her, Leo eventually dumps her by not taking her to the school dance.

In the end, it is better for Stargirl to move away than keep going to MAHS. Because Leo is the main character, he is left behind to analyze his behavior along with his professor friend Archie. Archie makes sure that Leo understands some things after Stargirl leaves town. First, he reminds Leo in chapter 32 that Stargirl really liked him. Then he makes sure Leo knows that she changed her whole lifestyle and personality just so he would feel better about being with her in public. In fact, Archie says the following:

"Gave up her self, for a while there. She loved you that much. What an incredibly lucky kid you were" (178).

Leo claims that he knows he was lucky to have dated Stargirl, but Archie claims that he really couldn't know now, but someday, maybe he would. Leo responds inwardly by thinking the following:

"I knew he was tempted to say more. Probably to tell me how stupid I was, how cowardly, that I blew the best chance I would ever have. But his smile returned, and his eyes were tender again" (178).

This conversation between Leo and Archie validates that Leo is the main character because it is he who has the biggest struggle to overcome, not Stargirl. Leo is the one who must learn the most from his relationship with her and it is he who must conquer his own insecurities among his peers regarding social status, conformity, and acceptance.