The Sustainable Development Goals (SDG) address, among other global concerns: health and well-being for all (goal 3); gender equality (goal 5); and the reduction of inequality within and among countries (goal 10). Gender refers to the socially-constructed characteristics of women and men, in all their diversity, while sex refers to purely biological differences. Gender equality is sometimes understood narrowly as concerning only the differences between women and men. To achieve health and well-being for all, a more compelling and nuanced understanding of gender is needed.