In order to contextualize the Brazilian and Chilean cases, this chapter surveys the various ways in which Latin America’s political parties have shaped the two interlinked dependent variables of this study: women’s political participation and the formation of state gender policy. Parties are both gendered organizations that reflect the gender ideology of their membership and leaders through their internal culture and practices, and gendering institutions that act as gatekeepers, framing, encouraging or restricting women’s political agency as party supporters, activists, leaders, candidates and representatives, and (re)producing normative conceptions of gender relations through their electoral campaigns, party policies and legislative activity. Much analysis focuses only on ideology, especially the left—right axis, whereas I propose closer attention to three overlooked independent variables: the intersection of the left—right cleavage with the secular-religious one in the region’s party systems; the gendered political habitus that develops within individual parties and how this is sustained by practices of gendered political sociability; and the type as well as the degree of party institutionalization. These variables, in combination, determine the permeability of individual parties and party systems to gender issues.