High School Musical 3: Senior Year will be the next installment in Disney's popular High School Musical franchise. It is being scheduled for a theatrical release on October 24, 2008. Kenny Ortega returns as director and choreographer and all six primary actors from the previous two films will reprise their roles.

Now high school seniors, Troy Bolton (Zac Efron) and Gabriella Montez (Vanessa Hudgens) are facing the prospect of being separated from each other as they go off in different directions when graduating from East High. Joined by the rest of the Wildcats, including Sharpay Evans (Ashley Tisdale), Ryan Evans (Lucas Grabeel), Chad Danforth (Corbin Bleu), Taylor McKessie (Monique Coleman), they stage an elaborate spring musical reflecting their experiences, hopes and fears about the future.

An international casting call went out to find three new sophomore "Wildcats". This resulted in the casting of Matt Prokop, Justin Martin, and Jemma McKenzie-Brown. Commenting on the announcement, Ortega said, "Peter Barsocchini’s exciting script for ‘High School Musical 3’ called for the addition of three sophomore characters, so we set out on a massive casting search across North America and England to find just the right young actors to play the parts. We think these talented performers will bring lots of humor, new twists, and musical fun to the film. Jemma was one of the many young actresses that we met in London, and she impressed us with her singing and dancing, in addition to being very exciting and effervescent. Matt has a terrific personality, and a great sense of comedy and fun. And Justin had a great presence and charisma, besides being a wonderful comedic actor who could really dance. I am confident that the three new actors joining our original cast will help to bring great musical thrills, surprises and a lot of fun to Senior Year and the halls of East High."

The motion picture soundtrack will be released on October 21, 2008.

The first song off the soundtrack, "Now or Never", debuted on Radio Disney on July 11, 2008.

In February 2007, Disney announced plans for a 2008 feature film sequel with a Halloween theme dubbed "Haunted High School Musical." In September 2007, Disney announced that they had scrapped plans for the Halloween theme and instead will focus on the senior year of key characters at East High. According to Yahoo news, the original writer from the first two films, Peter Barsocchini, is writing the script for the third part in the High School Musical series. The original producers and director/choreographer Kenny Ortega are also on board, which Ortega confirmed in an interview with Access Hollywood.

Zac Efron was quoted in People Magazine as saying, "I can tell you that if the script is good and if we all agree on a final script, then there's nothing that is going to hold us back from doing it. We have fun making these movies and that's very rare in this business."

Rumors persisted of ongoing salary disputes between Disney and the lead performers, particularly Efron. According to Rachel Abramowitz, as reported online by the Chicago Tribune, "an eclectic cross-section of Hollywood insiders think Efron should get a cool $5 million for High School Musical 3, the theatrical version of the franchise, which Disney hoped to make before the Writers Guild and Screen Actors Guild strike shut down Hollywood for several months. Efron declined to comment for the article, and although contract negotiations still are ongoing, sources say Efron is being offered a salary closer to $3 million, not $5 million, for the follow-up, which focuses on senior year at East High. Whatever the price, he's still perceived as a steal."

Ortega stated that pre-production would most likely start in January 2008. Filming began May 3, 2008, at East High School in Salt Lake City, Utah. He stated that the script had been submitted before the Writers strike started and that they were developing music. He added that filming will happen in Salt Lake City, Utah (as the first two films), hinted that the plot will be something of the nature of the Wildcat's final year in High School and stated "it looks like we've rounded up the cast."

Before filming began, the HSM3 board and cast held a press conference at East High School announcing the start of filming. The movie will be released in theaters (in the USA) on October 24 of that year, though several countries like Great Britain will get to see the movie at least one week earlier. The film has a $13.3 million dollar budget and a 40-day shooting period. This film is said to be the final installment with the current cast.

On July 13, 2008, the official trailer premiered on Disney Channel and ABC Family. It also premiered on Disney Channel Latin America the same day, and on internationals Disney Channels on July 14, 2008.

Despite early speculation that Vanessa Hudgens would be dropped from High School Musical 3 due to her nude photo scandal, The Walt Disney Company denied the reports, saying, "Vanessa has apologized for what was obviously a lapse in judgment. We hope she's learned a valuable lesson."

Although it was reported by OK! Magazine that Vanessa would be replaced by Adrienne Bailon or Sabrina Bryan from the Cheetah Girls in High School Musical 3, Access Hollywood confirmed that the cast was still in negotiations and Vanessa would not be cut from High School Musical 3. Vanessa's representative quoted, "Totally untrue. It is an old rumor," the representative told Access, "OK! Magazine never bothered to check the fact with me, but they did call Disney who said it wasn’t true, but yet OK! ran it anyway. Apparently, OK! Magazine was having a slow news day."

According to documents filed with the Utah Governor's Office of Economic Development board (GOED), Utah will again be the setting for HSM3. Shooting is scheduled to begin from April 21, 2008, and is expected to be complete by June 13, 2008. Lisa Roskelly, spokeswoman for Governor Jon Huntsman, Jr. said, "[The third] High School Musical will be officially shooting in Utah." According to the Salt Lake City Tribune, "...to help lure the production back to where it all began - at Salt Lake City's East High School - the GOED board Friday approved a maximum $2 million incentive for the production, the largest ever given to entice a filmmaker to Utah."

Filming was eventually pushed back and began on May 3, 2008. The 41 days scheduled for shooting is a longer period than for the first two films. Disney had declined comment on whether or not East High School would be used for shooting again, but the school board had revealed they met with Disney.

The winner of ABC's summer reality show, High School Musical: Get in the Picture will appear in a music video that is shown over the end credits of the theatrical release of the film.