This paper is concerned with the historical roots of gender equality. It proposes and empirically assesses a new determinant of gender equality: gender-specific outside options in the marriage market. In particular, enlarging women's options besides marriage-even if only temporarily-increases their bargaining power with respect to men, leading to a persistent improvement in gender equality. We illustrate this mechanism focusing on Belgium, and relate gender-equality levels in the 19th century to the presence of medieval, female-only communities called beguinages that allowed women to remain single amidst a society that traditionally advocated marriage. Combining geo-referenced data on beguinal communities with 19th-century census data, we document that the presence of beguinages contributed to decrease the gender gap in literacy. The reduction is sizeable, amounting to a 12.3% drop in gender educational inequality. Further evidence of the beguinal legacy is provided leveraging alternative indicators of female agency.