The original 'Harry Potter' stars are reuniting for a TV special.

Daniel Radcliffe is reuniting with his former co-stars

Daniel Radcliffe is reuniting with his former co-stars

Daniel Radcliffe, Emma Watson and Rupert Grint are all reuniting for 'Harry Potter 20th Anniversary: Return to Hogwarts', which will air on HBO Max on January 1.

HBO explained that the programme will "tell an enchanting making-of story through all-new, in-depth interviews and cast conversations".

A host of other cast members will also appear in the upcoming special, including Ralph Fiennes, Helena Bonham Carter, Robbie Coltrane, Gary Oldman, Tom Felton, and Imelda Staunton.

Tom Ascheim, the president of Warner Bros. Global Kids, Young Adults and Classics, said: "It has been an incredible journey since the debut of the ‘Harry Potter and the Sorcerer’s Stone’ film, and witnessing how it has evolved into this remarkable interconnected universe has been magical to say the least.

"This retrospective is a tribute to everyone whose lives were touched by this cultural phenomenon - from the talented cast and crew who poured their heart and soul into this extraordinary film franchise to the passionate fans who continue to keep the wizarding world spirit alive 20 years later."

The TV special is being executive produced by Casey Patterson of Casey Patterson Entertainment.

Looking forward to the HBO show, Casey said: "There’s magic in the air here with this incredible cast, as they all return home to the original sets of Hogwarts, where they began 20 years ago.

"The excitement is palpable as they prepare to take their fans on a very special and personal journey, through the making of these incredible films."

The 'Harry Potter' film series was based on the eponymous novels by JK Rowling, and is still one of the highest-grossing movie franchises of all time.