Scarlett Johansson is suing Disney for breach of contract for streaming her film Black Widow at the same time as its cinema release.
The superhero film set a box office record for the Covid-19 pandemic when it came out this month, grossing $218m (£157m) on its first weekend.
But box office receipts then fell sharply and Ms Johansson argues she was deprived of potential earnings.
In response, Disney said it had “fully complied” with her contract and that her case had “no merit whatsoever”.
Disney said In a statement that her legal action was “especially sad and distressing in its callous disregard for the horrific and prolonged global effects of the Covid-19 pandemic”.
Ms Johansson said she was promised by Marvel Studios, which is owned by Disney, that Black Widow would be a “theatrical release”.
She said she had understood this to mean a “window” of time would pass before it would be streamed – a period that has traditionally lasted 90 days.
Black Widow took some $80m in ticket sales in North America and $78m internationally, plus at least $60m in Disney+ Premier Access rentals on its first weekend.
Sources close to the actor, whose salary was based on the box office performance of the film, project that she lost $50m, according to media reports.