The celebrated British actor, 53, will play Captain Lorca in forthcoming CBS All Access drama Star Trek: Discovery when it launches with a 13-episode run over the summer.
But while Isaacs will feature prominently as captain of Federation starship USS Discovery, his role will be overshadowed by that of Lieutenant Commander Rainsford, played by The Walking Dead’s Sonequa Martin-Green.
Developed as a precursor to the hugely popular franchise, the new series will take place some ten years before the events of the original Star Trek – which made stars of leading man Shatner and co-star Leonard Nimoy following its launch in 1966.
It is also the franchise's first offering in 12-years following the cancellation of poorly viewed spin-off Star Trek: Enterprise in 2005.
'It’s important to get it right,' CBS Chairman Les Moonves said in a statement. 'Star Trek is the family jewels. We’re not going to rush it in. There’s a lot of post-production. But I’m very confident based on what I’ve seen so far.'
Tweeting on Tuesday, Isaacs confirmed his casting by sharing a snap of the captain’s chair with the accompanying tweet: ‘Nice chair. Hope it’s comfy.’
Shatner and Stewart both enjoyed enormous success after taking on their respective roles as Captain's James T. Kirk and Jean-Luc Picard.
The classically trained Stewart, 76, became the franchise's first British captain after taking a starring role in Star Trek: Next Generation over seven seasons and four films.
Uncharitably referred to as the 'unknown Shakespearean actor' by a dubious Los Angeles Time shortly after his casting, the actor became an instant hit with fans - despite harbouring initial doubts about the show's longevity.
Isaacs is already well known on US shores thanks to his role as wizarding nemesis Lucius Malfoy in the Harry Potter franchise, but his reception as Lorca will ultimately be determined when the show airs.
Other stars to feature in a largely ensemble cast include Doug Jones as science officer Saru, James Frain as Sarek, Spock's Vulcan astrophysicist father, former Bond girl Michelle Yeoh as captain Georgiu and Chris Obi as a Klingon leader T'Kuvma.
The newest 'Star Trek' captain: Jason Isaacs
Lucius Malfoy is about to boldly go where no one has gone before.
British actor Jason Isaacs, perhaps best known in America for playing Draco's dad in the Harry Potter franchise, has signed on to play Starfleet's newest captain in CBS All Access' upcoming Star Trek Discovery.
All we know so far about Isaacs' character is his name: Captain Lorca. Oh, and we know what his chair will look like.
The show, which takes place approximately a decade before the events of the original series, will feature one familiar character: Spock's father Sarek, played by James Frain (Gotham, True Blood).
The cast also includes The Walking Dead's Sonequa Martin-Green as Lorca's second in command and 30 Rock's Maulik Pancholy as a Starfleet medical officer. Other roles include Terry Serpico (Army Wives) as a high-ranking Starfleet admiral, Michelle Yeoh (Crouching Tiger, Hidden Dragon) as another captain and Mary Wiseman (Baskets) as a cadet who will be assigned to Lorca's ship, the USS Discovery, after graduation.
Discovery, which began production in late January, will air its premiere episode on CBS before moving to its regular home on the subscription-based All Access platform, similar to the way The Good Fight launched in February. But the series has been beset by delays, and executive producer Bryan Fuller was relieved of his command. Originally due in February, the launch date was first pushed to May, and is now planned for late summer or early fall.
Last month, CBS chief Leslie Moonves told the audience at a Morgan Stanley investor conference that he wasn't worried by the delays: “It’s important to get it right, and ‘Star Trek’ is the family jewels.”
Jason Isaacs: Harry Potter's Lucius Malfoy is probably advising Donald Trump on immigration
He may have hung up his robes and silver wig in 2011 but Jason Isaacs has his own theory about what his Harry Potter character Lucius Malfoy is most likely up to in 2017.
"I think Lucius and Nigel Farage would be advising Donald Trump on immigration policy" the actor chuckles as he reveals the future he'd write for the man of Malfoy Manor if JK Rowling handed him the pen.
Isaacs, who spent close to a decade in the role of Draco Rowling's Death Eater father, is quite the fan of Rowling's Potter tales, and has often spoken at length about how eager he was to become a part of the story when he arrived on set for Chamber of Secrets.
"I do remember most vividly my first day doing a proper scene because it was with Richard Harris, who was a huge hero of mine" he tells RadioTimes.com beneath the twisted tree roots of soon-to-be opened Forbidden Forest extension at the Warner Bros. Studio Tour.
"It was the last scene from Chamber of Secrets and there were all sorts of magical things that happened."
Isaacs is particularly tickled by an exchange he had with director Christopher Columbus as they prepared to shoot another take of the sequence. Columbus suggested Isaacs shut the door behind him and when the actor made a simply query, he was genuinely enchanted by the director's answer.
“I asked ‘can I just wave my hand and the door shuts by magic?’ and he went ‘yeah, sure’. And I thought ‘this is going to be awesome’”, Isaacs beams.
The actor says "it's a real privilege" to be a part of Rowling's story and the universe she has created, recalling meetings with fans for whom Harry Potter's journey provides real hope and inspiration.
And he agrees that it's a tale with themes that, in the current political climate, have possibly never been more important for the generation that grew up with the Boy Who Lived.
"It is a single powerful story about tolerance and inclusion and at the time she was wriitng it, it must have seemed to some people about the rise of fascism or the Second World War, but clearly it’s so much more universal that even 50 years later. It has so many contemporary applications and that’s why she’s a brilliant story-teller. She takes important themes of life and love and loss, tolerance and politics and how those things are intertwined. And she wrote something that is applicable at all times. But you’re right, never more so than now."
Would he ever be tempted to become a part of Rowling's story once again, then, given the opportunity to jump back into Lucius Malfoy's robes?
“I wouldn’t mind. I would love if regularly they’d go ‘it’s that time of year again, throw a wig on and come mince around for a while" he laughs.
"But you know I had a good long run and it was great. What we did, what I love about what we did was it was perfect. It was the books, it was a single story told in eight films, with a beginning, middle and end, and I’m glad that nobody tried to milk it further. They’re too tasteful to do anything like that.”