Johansson's Black Widow aka Natasha Romanoff died in "Avengers: Endgame" this year.
During an appearance on "The Tonight Show Starring Jimmy Fallon", the actress asserted that her Marvel character is really dead.
The actress said she had just finished filming "Black Widow", a prequel, in London, reports dailymail.co.uk. The film is slated to release in 2020.
She described shooting for "Black Widow" as a cathartic experience, especially since she had been grappling with her character's death.
"It brought a closure to me that I needed, because I was kind of wiped out after that last one emotionally and literally," she said.
Many fans didn't want to believe her character was gone. She acknowledged it, and said some had even tried to convince her that Black Widow existed in an alternate universe.
"But no, I think death is the final thing," she added.
"Black Widow" is set after the events of "Captain America: Civil War" but before the events of "Avengers: Infinity War". The film will trace the story of Romanoff, who will confront her past.
It is being reported that actor Robert Downey Jr will be back as the enigmatic superhero Iron Man in the Marvel Cinematic Universe with "Black Widow". The characters will be back as "Black Widow" is a prequel taking place ahead of the events of "Endgame". It's unknown how big Downey Jr's role in the film will be.
( With inputs from IANS )