Board Thread:General Discussion/@comment-24100805-20160201152915/@comment-32182236-20181203175358

Chikorita Lover wrote: I'm pretty sure Frisk's a girl. In some routes, you go on dates with Papyrus and Sans, who we all know are boys.

You also obtain the Old Tutu and Ballet Shoes, and boys probably wouldn't want to wear that. Of course, some boys would, similar to how I'm a boy whose favorite color's pink, which is associated with girls.

Frisk's most likely a girl, but Chara's a whole other story, as we don't see many gender-associated actions and preferences of theirs. However, at the end of a soulless pacifist route (pacifist route after genocide), choosing to stay with Toriel plays a lower-pitched laugh at the end. This laugh most likely belongs to Chara, so Chara may be a boy. You also go out with Alphys. No matter which gender they are, that means they go out with someone both of their own gender and the opposite one. (And besides, why can't Frisk be gay? We already have a lesbian pair!)

You can also obtain the Cowboy Hat. Boy's clothing.

So evidence suggests that they're a girl, AND that they're a boy. So, both can work out.

We really are meant to decide for ourselves. Frisk is our playable character.