Criminal prosecutors enjoy wide discretion in the decisions they make but are largely unstudied by empirical scholars. This paper explores gender bias in prosecutorial decision-making. I find that defendants are charged more leniently when they are the same gender as their prosecutor as opposed to when the defendant and prosecutor are different genders. Such gender-based favoritism at the charging stage ultimately translates into differential outcomes in sentence length. Gender-based leniency, however, is not uniform across all geographic areas, all types of cases, and all defendant characteristics. Examining heterogeneity on many dimensions suggests that prosecutors’ social preferences are more likely to explain gender-based leniency than differences in how male and female prosecutors work. I conclude by discussing how prosecutor offices might address gender favoritism.