Childhood gender nonconformity has been associated with numerous adverse experiences, including peer bullying and homophobic violence. However, little is known about gender nonconformity in the context of intimate relationships, independent of sexual orientation. This study aimed to examine associations between childhood gender nonconformity and intimate partner violence (IPV) in adolescence and early adulthood. Using data from the 2007 wave of the U.S. Growing Up Today Study (N = 7,641, mean age = 22.8 years), we estimated risk ratios (RRs) for the association of gender nonconformity up to age 11 years and lifetime IPV victimization and perpetration. Models were adjusted for demographic characteristics, including sexual orientation identity. We assessed effect modification by gender and examined whether childhood abuse mediated the association between nonconformity and IPV. Males in the top decile of nonconformity were at elevated risk of IPV victimization (RR = 1.40, 95% confidence interval [CI] = [1.15, 1.71]) and IPV perpetration (RR = 2.34, 95% CI = 1.54, 3.56) compared with those below median nonconformity, adjusting for sexual orientation and demographic characteristics. There was no evidence of a similar association for females in the top decile of gender nonconformity. Childhood abuse did not mediate IPV disparities by gender nonconformity. We identify gender nonconformity as an important risk indicator for IPV victimization and perpetration among young adult males, independent of sexual orientation. Findings highlight the vulnerability of boys and men who do not conform to societal gender norms and the importance of studying gender expression as a determinant of violence. IPV prevention efforts may be improved with more explicit focus on socially constructed gender norms and support for diverse gender expressions. Further research into the pathways between nonconformity and IPV and in more diverse populations is needed to build a more comprehensive understanding of the unique experiences gender nonconforming youth face.