The cast will come back together for a charity fundraiser in Los Angeles in December, which has been spearheaded by Monique Coleman (who played Taylor McKessie) and her GimmeMo' Foundation.
Premiering in 2006, High School Musical centred around popular high school basketball star Troy (Zac Efron) and academically gifted newcomer Gabriella (Vanessa Hudgens), who both discover their mutual love for music.
The cast returned one year later for High School Musical 2 and later filmed High School Musical 3: Senior Year in 2008.
Favourites from the contemporary teen musical including Vanessa, Ashley Tisdale, Corbin Bleu, Lucas Grabeel, Kaycee Stroh and Olesya Rulin, will all take part. Sadly, Zac will not be able to attend due to work commitments, but will be recording a special video message for the occasion.
Taking to Twitter last night (24 October), Zac said: "Thanks for organising the #HSMreunion @gimmemotalk! Sorry I can't be there, but I support your cause. Proud of you Mo!"
Vanessa later tweeted: "Can't believe it's been 5 years since HSM 3!"
Rumours about a reunion had been circulating on social media in recent weeks, but it was confirmed yesterday in a YouTube video posted by Monique. She said: "The rumours are true, but it's not for a new movie... it's for a cause."
Relive some High School Musical memories and check out the cast performing 'All For One' in the video below: