Same here. Like many others I maybe defined the question too narrowly. To me someone who is largely famous for their looks is someone like a supermodel or someone who is not very talented in their nominal job, but is well known regardless because they are still attractive. Actual decent actors and musical acts wouldn’t apply.
Farrah Fawcett Majors.
mmm
I was able to do it, but MOST of the ones I think of as in their 20s are now in their 30s.
Nope. Billie Eilish immediately sprang to mind, but she doesn’t meet the criteria. Ariana Grande came to me next, but not within the time limit.
Nope. But that’s not because of ages; it’s because I tend to avoid celebrity culture.
I went with the Hadid sisters (Bella and Gigi). Since their only celebrity is for modeling I think they count.
When it comes to the younger generation of performers in any category, I might be familiar with names, I might recognize some faces, tho not with associated names. So my answer was a resounding NOPE!
Mark Harmon, on the other hand, is still some serious eye candy!
Not even close. I figured out a name in 2 seconds but he was 54 years old. Yes, I feel kind of stupid.
That’s very likely the case, but is not what the OP asked. It asked if they are mostly known for looks.
Turner is not particularly prettied up for most of “Game of Thrones,” and was already quite famous when she was a child. Lawrence vaulted to fame with her Oscar-nominated turn in “Winter’s Bone,” a very unglamorous role. She is beautiful and well known for it, but I maintain her acting skills remain her primary source of fame.
As Jophiel points out, and I missed, there are indeed some actresses who really are just known for their looks, like Megan Fox.
Even if Eilish was two years older, she is most definitely not primarily known for being beautiful or sexy. I would submit that there is no woman in the popular music industry today who is more determined and successful at hiding her looks and succeeding purely on musical merit than is Billie Eilish.
Nope. I guess I’m officially old now 
Where I failed was the ‘in their twenties’ part. If presented with a list of celebrities, I couldn’t peg their ages within 10 years without some thought, and I’d probably be wrong.
How do I know who’s in their 20s without taking the 2 seconds to google them?
Kylie Jenner immediately came to mind. And that’s only because Yahoo news is constantly telling me how hot she is.
I couldn’t in two seconds.
Most of the pretty young girls I could think of are known for being singers or actresses.
First name I could come up with, while writing this, is some instagram model I keep seeing in Reddit named Sabrina Lynn. But then again, I have a thing for redheads.
Does thinking of “Whoever the youngest Kardashian kid is” count?
Just got this on my yahoo feed today:
Kylie Jenner Wears Sexy Curve-Hugging Red Outfit for Valentine’s Day Party
Kate Upton - just checked, she’s 27, so I picked yes. Mainly known as a swimsuit model, and her few acting roles are primarily of the “hot chick” variety.
Heh, I thought of Kim Kardashian and Chris Hemsworth, then looked them up to find they are both nearly 40.
At least I didn’t say Mary Pickford.
That’s a good call.
Billie Eilish isn’t in her twenties, though, and is definitely not known for being good-looking or sexy. I mean, she’s not ugly or anything, but she’s known for her music, not for being sexy. Ariana Grande is definitely known for her looks, but not “largely.”