I propose, defend and illustrate a principle of gender justice meant to capture the nature of a variety of injustices based on gender:A society is gender just only if the costs of a gender-neutral lifestyle are, all other things being equal, lower than, or at most equal to, the costs of gendered lifestyles.The principle is meant to account for the entire range of gender injustice: violence against women, economic and legal discrimination, domestic exploitation, the gendered division of labor and gendered socialization. The sense of “costs” employed is similarly wide. Costs can be material (such as financial, time or effort), psychological (such as self-respect, a good relationship with one’s body and emotions) and social (such as reputation...