The film is about Princess Diana's existential crisis during the Christmas of 1991, as she considers divorcing Prince Charles and leaving the British royal family.

Among the attendees is Diana, Princess of Wales, whose marriage to Prince Charles has become strained due to his affair with Camilla Parker Bowles.

On Christmas Day, Diana attends a service at St Mary Magdalene Church, Sandringham, where she notices Camilla among the gathered crowd and is photographed by numerous intrusive journalists.

She holds a difficult conversation with Charles, who rebuffs her concerns over William and Harry's participation in a pheasant shoot the next day, and advises her to develop a stronger sense of separation between her public and private lives.

Diana responds by stating that she never asked anyone to die for her and accuses him of planting the Boleyn book in her room as a warning, which he denies.

After bidding Maggie farewell, Diana goes to the pheasant shoot, walks out in front of the crowd of hunters, and announces that she is taking William and Harry to London, to which Charles reluctantly agrees.

[4] Filming began at the Schlosshotel Kronberg, Germany, in January 2021 with Timothy Spall, Sally Hawkins, and Sean Harris joining the cast.

During the fall of 2020, Larraín and Production Designer Guy Hendrix Dyas embarked on an intense scout in search of the perfect location.

Somewhere where you wouldn't necessarily enjoy spending Christmas, where you get the subtle feeling that underneath the festivities there's a real anguish and misery at play.

She also revealed that she and Larraín reviewed sequences from various Stanley Kubrick films such as Barry Lyndon (1975) and A Clockwork Orange (1971) to learn about the style of camera movement, rhythm of the shots, and the use of short focal lenses.

In some scenes where they wanted to minimize the grain, they opted for the 35mm film stock as it retains both softness and details on the darker part of the image.

[31] Upon the teaser trailer's release, Forbes reported that the role "thrusts" Stewart "into the Oscar race" for the Academy Award for Best Actress.

[32] After the film's world premiere, Variety also stated, "There's already been plenty of talk in Venice that the role will likely land Stewart her first Oscar nomination."

The film received a three-minute standing ovation at its world premiere,[33] with critics lauding Stewart's performance as Diana.

The website's critics consensus reads: "Spencer can frustrate with its idiosyncratic depiction of its subject's life, but Kristen Stewart's finely modulated performance anchors the film's flights of fancy.

"[38] Drawing comparisons between the film and the Jacqueline Kennedy biopic Jackie (2016), also directed by Larraín, Pete Hammond of Deadline Hollywood stated that "Spencer is something else indeed, almost playing out in a conventional dramatic fashion, a more accessible approach in some ways, but also more ambitious as it is squarely from the point of view of its title character, purposely called Spencer to assure us that the person who once was, is well on the way to finding that very lost spirit again before it is too late.

Former Royal Chef Darren McGrady, who was portrayed by actor Sean Harris in the film, said, "Kristen Stewart is amazing as the princess, with her mannerisms and her voice ... the happy scenes of her with the boys, it was like her coming alive again.