The Oscar-nominated star of films including The Dark Knight and Secretary and television series including The Honorable Woman made the revelation in an interview with The Wrap magazine, a portion of which was published this week.

While her male contemporaries like Bradley Cooper or Leonardo DiCaprio, both 40, continue to be cast opposite actresses in their 20s, Gyllenhaal said her age had been a barrier to a recent role, even though her potential co-star was 18 years her senior.

"There are things that are really disappointing about being an actress in Hollywood that surprise me all the time," Gyllenhaal told the magazine.

"I'm 37 and I was told recently I was too old to play the lover of a man who was 55. It was astonishing to me."

Gyllenhaal did not reveal the name of the co-star or the project.

"It made me feel bad," she said, "and then it made me feel angry, and then it made me laugh."

Culture website Vulture observed in 2013 that "as leading men age, their love interests stay the same," in an analysis that looked at the age disparities in Hollywood films. They found Harrison Ford is routinely paired with women 20 or 30 years his junior, from 29-year-old Anne Heche in Six Days, Seven Nights, when Ford was 55, to 39-year-old Kristin Scott Thomas in Random Hearts, when Ford was 57.

Johnny Depp, Tom Cruise and Denzel Washington were also named as stars in their late 40s or 50s who are routinely cast opposite women in their 20s and 30s.

It is not just the scarcity of romantic roles, but indeed any roles, for women in middle age that is a problem, according to some actresses. Kristen Scott Thomas, now 54, recently said the dearth of roles for women her age was a "disaster."

"I won't bore you with all the stories of older women not getting jobs in film because it's so boring. But it's true. It's a disaster," she told London's Daily Telegraph.

Though there are rare exceptions, the phenomenon of women over 40 no longer being considered for leading, romantic parts was skewered in a recent episode of Inside Amy Schumer, which showed Tina Fey, 44 and Patricia Arquette, 47 at a picnic with Julia Louis-Dreyfus, celebrating the 54-year-old actress' "Last F..kable Day".

"In every actresses' life, the media decides when you finally reach the point where you're not believably f..ckable any more," Louis-Dreyfus says.

"You know how Sally Field was Tom Hank's love interest in Punchline and like, 20 minutes later she was his mom in Forrest Gump?" said Fey.

Australian actress Rebel Wilson was outed in the media earlier this week for reportedly telling people she was 29, when she was in fact 35.

Gyllenhaal told The Wrap that she nevertheless remained optimistic about the prospects for interesting work in the future.

"A lot of actresses are doing incredible work right now, playing real women, complicated women," she said. "I don't feel despairing at all. And I'm more looking with hope for something fascinating."