Main characters

Troy Bolton (Zac Efron) is the male protagonist of the story and the captain of the East High Wildcats basketball team. His best friend is Chad Danforth. At a New Years party at a ski resort, he was pressured into singing 'Start of Something New' with Gabriella Montez; prior to that, he had only sung in the shower.[3] Troy is torn between basketball and singing; he wants to sing with Gabriella, but his teammates push him away from it with peer pressure and even trickery because they are worried it will affect their chances at winning the championship game, as Troy is the coach's son, Wildcat captain, and star player.
Gabriella Montez (Vanessa Anne Hudgens) is the female protagonist. She is a shy and intelligent student who just changed schools. She originally met Troy when they were forced into singing together at a New Years party at a ski resort. She meets him again when she moves to the same school as Troy in Albuquerque. She is hesitant to let everybody know of her past achievements, although they find out that she previously won numerous Scholastic Competitions. She had previously been in a church choir, but passed out after having everybody stare at her while singing solo. She and Troy audition, get a callback, and then win the lead parts for the Winter musical. She also helps East High win the Scholastic Decathlon.
Sharpay Evans (Ashley Tisdale) is the antagonist of High School Musical. She is an arrogant person who always wants her way. She, along with her brother Ryan, audition for the winter musical against Troy and Gabriella. When she hears that Troy and Gabriella have a callback, she changes the callback date so Troy and Gabriella wouldn't be able to get the leads. Sharpay ends up being the understudy for Gabriella, and in the end, wishes Gabriella good luck by telling her to break a leg. Chad, at one point, calls Sharpay a "show dog"; the Shar Pei, a homophone of Sharpay, is a kind of dog.
Ryan Evans (Lucas Grabeel) is Sharpay's fraternal twin brother, acting partner, and nicer one of the twins. They have starred in seventeen productions together. Ryan isn't very smart, as shown by his inability to read "Go Drama Club!" on the basketball team's shirts. Ryan has a taste for hats, wearing nine different during the movie.
Taylor McKessie (Monique Coleman) is the leader of East High's science club, which competes in the Scholastic Decathlon. She befriends Gabriella when she arrives to the school and convinces her to join the Scholastic Club. While she at first tried to stop Gabriella from singing, she eventually ended up supporting her. She has a strong dislike for athletes, stating that they "contribute nothing to society other than slam dunks and touchdowns." However, her opinion of athletes changes over time. She is asked out by Chad Danforth by the end of the film.
Chad Danforth (Corbin Bleu) is a member of the Wildcats team and Troy's best friend. He seems to be extremely devoted to basketball. From the start, he's a little selfish and unsupportive of Troy's auditioning for the musical. He thinks that the musical isn't for basketball players. However, he realizes later that singing is something that Troy truly enjoys and so Chad gives his support to his best friend's audition endeavor. After teaming up with Taylor McKessie to pull Troy and Gabriella apart, and then to put them back together again, he asks her out.

Minor characters

Ms. Darbus (Alyson Reed) is the drama teacher at East High. She is an advocate of theater and has a strong dislike for cell phones. She has gotten into arguments with Coach Bolton numerous times.
Coach Jack Bolton Coach Jack Bolton (Bart Johnson) is the Wildcats' coach and Troy's father. He is a former champion Wildcats player, and expects his son to follow in his footsteps. He has gotten into numerous heated arguments with Ms. Darbus.
Kelsi Nielsen (Olesya Rulin) is a pianist and the composer of the Twinkle Towne musical. Kelsi is not the most confident person, as shown when she tries to give input to how Sharpay sang 'What I've Been Looking For'. By the end of the movie, however, she stands up to Sharpay. Troy calls her the playmaker and she receives the game ball. At the end of the movie, there is an indication that Jason and she start going out.
Zeke Baylor (Chris Warren Jr) is a member of the Wildcats team, who secretly enjoys baking. He likes Sharpay, and in the end of the film Sharpay begins to have mutual feelings. Zeke baked cookies for her but ends up giving them to Ryan after Sharpay reacted negatively. He also baked the "pi" pie as a sign of good luck to the decathlon team; some fresh cookies to keep Troy calm when Troy is told about why Gabriella's avoiding him; and a creme brulee which he considers his masterpiece.
Jason Cross (Ryne Sanborn) is also a member of the Wildcats team. He is the strong, silent type, his only major line being said to Ms. Darbus, as well as several other lines in the movie. In the theatre version of HSM, he only has one line. He also appears to have a crush on Kelsi, when he stood behind her to help her make a basket, right before the film's last musical number.