Walt Disney Co. ’s latest Marvel movie “Black Widow” opened in theaters in the U.S. and on the Disney+ service on July 9. Scarlett Johansson stars in the film and has become an integral part of the Marvel universe since appearing as Black Widow in 2010’s “Iron Man 2.” The Academy Award-nominated actress has starred in dozens of films including, “Lost in Translation,” “Her” and “Lucy.”

Why is Scarlett Johansson suing Disney?

Ms. Johansson filed a lawsuit Thursday in Los Angeles Superior Court against Disney, alleging her contract was breached when the media giant released the film on its Disney+ streaming service at the same time as its theatrical debut.

Ms. Johansson said in the suit that her agreement with Disney’s Marvel Entertainment guaranteed an exclusive theatrical release. Ms. Johansson’s representatives reached out to Marvel before the pandemic in 2019, seeking assurance that “Black Widow” would have a theatrical-only release, according to the complaint. Her total salary for the project was based in large part on the box-office performance of the film, according to the lawsuit. It adds that Disney intentionally made the move to prevent the actress from “realizing the full benefit of her bargain with Marvel.”

The suit doesn’t specify how much she is suing Disney for. The decision to put the movie on Disney+ is projected to cost Ms. Johansson more than $50 million, a person familiar with details of her contract claimed.

“Black Widow” grossed $80 million at the domestic box office and $78 million overseas during its July 9 opening weekend and generated another $60 million from $30 at-home purchases on Disney+.

“Black Widow” grossed $80 million at the domestic box office and $78 million overseas during its July 9 opening weekend and generated another $60 million from $30 at-home purchases on Disney+.

Photo: Jay Maidment/Associated Press

What is Disney saying?

A Disney spokesman said Ms. Johansson’s suit had no merit and is “especially sad and distressing in its callous disregard for the horrific and prolonged global effects of the Covid-19 pandemic.”

The company said it fully complied with Ms. Johansson’s contract, adding that the releasing of the film on Disney+ with Premier Access “has significantly enhanced her ability to earn” more money than the $20 million she has received so far for “Black Widow.”

On Friday, the co-chairman of the Creative Artists Agency, Bryan Lourd, the talent agency that represents Ms. Johansson defended the star and called out Disney for attacking her character.

“They have shamelessly and falsely accused Ms. Johansson of being insensitive to the global COVID pandemic,” Mr. Lourd said in a statement.

How much money has “Black Widow” made in theaters and on Disney+?

During its July 9 opening weekend, “Black Widow” grossed $80 million at the domestic box office and $78 million overseas, and generated another $60 million from $30 at-home purchases on Disney+. It was the first time Disney broke out a film’s streaming performance in such detail.

Disney began releasing movies simultaneously on Disney+ and in theaters partly because of the Covid-19 pandemic, when theaters were closed or at limited capacity, and partly to boost its nascent service.

Scarlett Johansson has become an integral part of the Marvel universe since appearing as Black Widow in 2010’s “Iron Man 2.”

Scarlett Johansson has become an integral part of the Marvel universe since appearing as Black Widow in 2010’s “Iron Man 2.”

Photo: chris delmas/Agence France-Presse/Getty Images

Why is this lawsuit important in Hollywood?

The suit could be a bellwether for the entertainment industry. Major media companies are giving priority to their streaming services in pursuit of growth and are increasingly putting their high-value content on those platforms.

“This will surely not be the last case where Hollywood talent stands up to Disney and makes it clear that, whatever the company may pretend, it has a legal obligation to honor its contracts,” said John Berlinski, an attorney at Kasowitz Benson Torres LLP who represents Ms. Johansson.

The issue also has implications between cinema owners and studio owners. At the end of March, theater owners were upset to learn of Disney’s decision to release “Black Widow” both in the cinema and on its Disney+ streaming service for an additional $29.99 fee. Disney also delayed the film’s release to July.

The launch of Disney+ has brought a bit of magic to a company whose stock had taken a nosedive after the coronavirus shut down theme parks and movie theaters. WSJ explains how Disney’s streaming platform has become a top competitor in an already crowded field. Photo illustration: Jacob Reynolds/WSJ The Wall Street Journal Interactive Edition

Write to Joe Flint at joe.flint@wsj.com and Talal Ansari at Talal.Ansari@wsj.com