Oscar-winning actor Thompson, 67, said older women are compelling, relatable and interesting, and should be at the heart of more films.
"Women are half the population and we get older. So, where are the stories about us?" she said.
"The older we get, the more interesting we are.
"I want to see more films centre ageing women; we are compelling, relatable and overdue for centre stage.
"Older women don't need permission to exist on screen. They already exist in the world, cinema just needs to catch up."
The research found that among the 100 highest-grossing films released in the UK for 2023, 2024 and 2025, six featured a "Chris" in the leading role, including Pratt and Hemsworth.
In contrast, only five starred women over 60 as the lead character - including Demi Moore, Diane Keaton and Jamie Lee Curtis, campaigners said.
"It is absolutely ludicrous to think so few films have been made in recent years that have an older woman at the front and centre," said Carole Easton, chief executive at the Centre for Ageing Better.
She called on people to "push back against ageism, and its intersection with sexism, by telling the cultural gatekeepers that we want all aspects and stages of life represented in the things we watch, listen to and read".
