Julie Mellor is to step down after six years as chairwoman of the Equal Opportunities Commission.
Mellor will become a partner at PricewaterhouseCoopers at the beginning of July.
Jenny Watson, deputy chair of the commission, praised Mellor for putting the gender pay gap on the map and helping to create a growing will among key players to close it.
"She has been a strong advocate of gender equality for both women and men, particularly in promoting and supporting the changing role of fathers," Watson said.
Patricia Hewitt, secretary of state for trade and industry and minister for women, said: "The EOC has made great progress under Julie's leadership.
"I'd like to add my personal thanks to Julie for all she's done to ensure that gender issues remain firmly at the heart of the government's agenda."
Watson will take over her duties until the government appoints a new chairperson after the General Election.