Each beauty graces her own cover of Elle magazine's October/25th anniversary issue, which spotlights 25 superwomen in the 25-something age range, all photographed by Carter Smith.
"Dear John" star Seyfried, looking flirty on her cover in a Louis Vuitton wool halter dress with a watercolor bodice and plaid skirt, turns 25 in December, and although she's in a good place in life, she's already fretting about the future.
"The best thing is, I'm happy," observes Seyfried, who poses Twiggy-style for her feature in mod makeup, a Lisa Perry clear vinyl rain jacket, and a Chanel red-checkered cashmere sweater with matching bikini bottoms.
"The worst is that I'm scared; the scariest thing is that I know it can't be easy -- the years to come."
Fox, meanwhile, already finds life to be a challenge.
"When I talk about my husband [Brian Austin Green], I feel as if people roll their eyes," says the 24-year-old "Jonah Hex" star, who appears demure in minimal makeup and a nude-colored dress on the cover before revving things up inside with dotted Emporio Armani Underwear and an unbuttoned oversized Armani Jeans striped shirt.
Conrad, whose cover attire is a colorful jumper, makes it clear, however, that at 24, she's in no rush to settle down. "I was never that girl who just wanted babies," says the reality star/designer/novelist, who, inside the magazine, looks very Lohan in a gray Gucci blazer with matching pants and Ray-Ban aviators. "I wanted a career before all of that."
And for 27-year-old Sidibe, being in your 20s is all about having fun -- even if it means lying about your age.
"Part of me thought it would be weird if people knew I was a grown-up playing a teenager in 'Precious.' So I had a twenty-first-birthday party," the "Big C" star, who wears a green Tadashi Shoji jersey cocktail dress with Fenton jewelry for both of her shots, says of marking her big two-five. "We had drinks and went to a strip club called Shotgun Willie's."
For more of Elle's favorite 25-somethings -- including Mila Kunis, Lauren Bush, and Camilla Belle -- pick up the new issue and visit the website.
In related news, check out Eva Mendes's loopy photo shoot for Vs. magazine.