The original cast of the Harry Potter series including Daniel Radcliffe, Emma Watson and Rupert Grint are set to reunite for a TV special 20 years after the first film screened.
HBO Max said the Return to Hogwarts will be released on 1 January 2022 – making a magical start to the New Year.
The trio will join American filmmaker Chris Columbus to discuss the films and explore their creation in depth.
Rowling, 56, was involved in the making of the films, with Warner Bros taking considerable notice of her desires – including the films being shot in Britain with an all-British cast.
The special was announced exactly 20 years on from the US release of the first film, Harry Potter And The Philosopher's Stone, on 16 November 2001.
Fans will be invited "on a magical first-person journey through one of the most beloved film franchises of all time", HBO Max said.
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A 52-second trailer featured clips from several Harry Potter films and promised "the legendary cast" would return "to where the magic started".
It will also include Helena Bonham Carter, Robbie Coltrane, Ralph Fiennes, Jason Isaacs, Gary Oldman, Imelda Staunton and Tom Felton – who all played key characters in the series.
Felton, who portrayed flaxen-haired villain Draco Malfoy, urged fans to save the date as he shared the trailer on Twitter.
He wrote: "Is this what school homecoming is like? Mark your calendars for New Years Day #ReturnToHogwarts, streaming on @hbomax x."
Matt Lewis, who starred as the hapless Neville Longbottom in the world famous films, posted: "This New Year's Day… we're putting the band back together."
Meanwhile, Watson, 31, shared a lengthy Instagram post to promote the special and 20th anniversary, and said Hermione Granger, who she played in the series, is her "favourite fictional character of all time".
She added: "I am proud not just of what we as group contributed as actors to the franchise but also as the children that became young adults that walked that path. I look at my fellow cast members now and I am just so proud of who everyone has become as people. I am proud we were kind to each other that we supported one another and that we held up something meaningful."
Executive producer Casey Patterson 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."
Buzz around the reunion comes as Radcliffe told a BBC documentary, also marking 20 years since the first film, of his joy that fans watch the Harry Potter films when they are "hungover and feeling really crappy about themselves".
"The time in most people's lives when they discovered it meant that it has an incredibly important place in a lot people's childhoods, and they still feel very protective over it," the 32-year-old actor said.
"One of my favourite fates that we could never have ever imagined for the Harry Potter films but that I have been told by several friends is that they are fantastic when people are hungover and feeling really crappy about themselves."
He continued: "They will just watch back-to-back a few movies and it just takes them to a place of warmth and comfort.
"That is so lovely to me. That is the real world effect that a film can have on someone's life. I think that is great."
Radcliffe also paid tribute to Rowling in the documentary, which is part of Movies With Ali Plumb.
Sky News reached out to Rowling's reps for comment.