This paper analyses how labour market concentration affects gender inequalities in wages, hirings, and working conditions. While theoretical models predict that firms will be able to extract a monopsony rent from workers who have lower geographical mobility, very specific skills, or specific working conditions' requirements, there is limited empirical evidence on this topic. Using French matched employer-employee data together with data on working conditions and a new definition of commuting zones that incorporates gender differences in mobility, we find that concentration in a given commuting zone and occupation increases the gender wage gap and decreases the share of women among new hires, but has limited effect on the gender gap in working conditions. Women with children and women of childbearing age are particularly affected by the increase in firms' monopsonistic power.