Recent work suggests that the stereotype associating brilliance with men may underpin women's underrepresentation in prestigious careers, yet little is known about its development and consequences in non-Western contexts. The present research examined the onset of this stereotype and its relation to children's motivation in 5- to 7-year-old Korean children (N = 272, 50% girls, tested 2021 to 2022). At age 7, children attributed brilliance to men when evaluating Asians and Whites, and girls became less interested in participating in intellectually challenging tasks than boys. Notably, this gender difference in interest was mediated by children's endorsement of the stereotype. The generalizable early emergence of the gender brilliance stereotype and its detrimental implications press the need to tackle gender imbalance in early childhood.