Taking over from Claire Foy (seasons one and two) and Olivia Colman (seasons three and four), Staunton joined the Netflix show in 2022 for its fifth series and will now take Queen Elizabeth to the story's planned conclusion at the end of season six.
But where else would viewers know the actress from?
Here's what you need to know about the esteemed star, where you may recognise her from, and what she's said about taking on the part.
Who is The Crown star Imelda Staunton?
Imelda Staunton is one of the UK's most highly-celebrated actors, with a career spanning theatre, television and film.
Born in January 1956, Staunton was the daughter of a labourer and a hairdresser. She was initially encouraged to take up acting by a teacher, and in 1974 landed a spot to train at the Royal Academy of Dramatic Arts (RADA). She graduated in 1976 and spent the next six years in English repatory theatre.
To begin with, her career was largely on the stage, and over the course of her career she has been the winner of four Olivier Awards – including three Lead Actress gongs for her performances in Into The Woods, Sweeney Todd and Gypsy.
Her first official screen role is credited as a small part in a 1982 episode of BBC2 Playhouse. Four years later she got a leading spot in the TV mini-series adaptation of The Singing Detective.
By the 2006 New Year's Honours, Staunton was awarded an OBE by Queen Elizabeth II for her contributions to drama. This was upgraded to a CBE ten years later.
Where would I have seen Imelda Staunton before?
As a star of stage and screen across a period of more than 40 years, Imelda Staunton has some impressive credits under her belt, affirming her as one of the UK's most beloved stars.
For many, Staunton is best known as the evil Dolores Umbridge in Harry Potter And The Order Of The Phoenix, the fifth instalment of the fantasy franchise.
She's also popped up in Downton Abbey alongside her real-life husband, appearing in the films as Maud Bagshaw.
However, other roles included her highly praised performance in Vera Drake, for which she was nominated for an Oscar in 2004 as Best Lead Actress. She lost out that year to Charlize Theron for Monster.
In film, other credits include Pride, Maleficent and its sequel Maleficent: Mistress of Evil with Angelina Jolie, Shakespeare In Love, and Paddington as the voice of the beloved bear's adored Aunt Lucy.
On TV, she had a longstanding role from 1995 to 1998 in TV series Is It Legal, and has also appeared in Little Britain, Cranford and Psychoville.
In 2019 she joined Martin Freeman as part of an all-star cast for ITV drama A Confession.
During lockdown, she joined the cast of Alan Bennett's Talking Heads, performing the monologue 'A Lady Of Letters'. Other participants that year included Jodie Comer, Martin Freeman, and Line Of Duty's Rochenda Sandall.
That same year, she joined the cast of Apple TV+ series, Trying, alongside Rafe Spall and Esther Smith as the kind-natured social worker Penny.
Unfortunately, due to commitments after being in The Crown, she bowed out of season three which aired in 2022.
Later this year, she will lend her voice to the Chicken Run sequel as Bunty in Chicken Run: Dawn of the Nugget.
What has Imelda Staunton said about being in The Crown?
Staunton made her first official appearance as Queen Elizabeth II in a "Royal Address" to confirm the start of filming on The Crown in September 2021.
As part of the speech, filmed on the set of Buckingham Palace, she said: "I'm delighted to be here, inheriting the role of Queen Elizabeth from two outstanding actresses. I will do my utmost to maintain the very high standard that they set.
"Hopefully I look calm, collected and capable… my stomach meanwhile, is doing somersaults."
Since then, the role has taken on a far more sombre tone following the death of the real Queen Elizabeth in September 2022. By that point, the cast was in the midst of filming the upcoming final season six, something Staunton didn't take lightly.
"We filmed that day, and then we got home and then discovered [what had happened] on the six o'clock, 6:30 news, so that was pretty devastating," she told Entertainment Weekly.
"I was relieved that I then [already] had a week off. Anyway, filming stopped. But it was odd, to say the least, and I'm glad I had time to regroup before I started again."
She has also spoken out in defence of the series, which has been criticised amid calls for it to include a disclaimer that The Crown is a work of fiction. Among the critics is Dame Judi Dench, who called the Netflix series "cruelly unjust" and "damaging" in an open letter.
Speaking on Woman's Hour back in 2021, shortly after her role was confirmed, Staunton said: "I think that is up to producers and directors.
"This isn’t verbatim; this isn’t taken from diaries. You’ve got to use your imagination, and I’d like to allow the audience a bit of intelligence. You can’t know that’s what Margaret and Elizabeth were talking about."
Part one of The Crown season 6 launches on Netflix on Thursday, 16 November with part two arriving on Thursday 14 December.