The burden of achieving gender equality is typically placed on women, limiting men's involvement in the movement. In contrast to work focusing on women's experiences as targets of discrimination, we propose a solidarity-based approach positioning men and women as agents of change, which relies on two key processes: leadership - particularly leadership as a form of influence based on shared identities among leaders and followers; and political solidarity as a way to mobilise the silent majority (men) to work as allies beside a minority (women) and embrace equality as a common cause for both groups. This thesis examines how to mobilise a broader audience for gender equality, and how leadership and social identity dynamics affect that mobilisation. Three empirical programs (totalling six experiments) investigate how best to increase women's and men's support for equality. Key independent variables of interest are leader gender, message framing, and social identity. Program 1 examines whether solidarity-based frames are more effective than traditional frames which focus on either fixing (Experiment 1; N = 338) or blaming women (Experiment 2; N = 336). Program 2 investigates how emphasising different levels of subgroup and superordinate identities (Experiment 3; N = 251; Experiment 4; N = 319) affects men's mobilisation. Program 3 investigates whether positioning men as being responsible for gender inequality (Experiment 5; N = 258), or being fellow victims of gender inequality (Experiment 6; N = 543) affects their mobilisation.