The masculine overcompensation thesis asserts that men react to masculinity threats with extreme demonstrations of masculinity, a proposition tested here across four studies. In study 1, men and women were randomly given feedback suggesting they were either masculine or feminine. Women showed no effects when told they were masculine; however, men given feedback suggesting they were feminine expressed more support for war, homophobic attitudes, and interest in purchasing an SUV. Study 2 found that threatened men expressed greater support for, and desire to advance in, dominance hierarchies. Study 3 showed in a large-scale survey on a diverse sample that men who reported that social changes threatened the status of men also reported more homophobic and predominance attitudes, support for war, and belief in male superiority. Finally, study 4 found that higher testosterone men showed stronger reactions to masculinity threats than those lower in testosterone. Together, these results support the masculine overcompensation thesis, show how it can shape political and cultural attitudes, and identify a hormonal factor influencing the effect.