This study investigated the contextual antecedents of the legal recognition of same-sex unions and marriages across 139 countries from 1988 to 2014. We pooled time-series data from various aggregate databases (i.e., SWIID, WDI, V-Dem, Polity IV, Archigos, and UIA database) to examine why laws protecting same-sex unions and marriages are more rapidly adopted by certain countries than by others. Within the frameworks of post-materialist values, world polity, and gender politics, we argue that economic development, along with memberships in international non-governmental organizations and female political participations, are some of the key factors propelling such legal reforms worldwide. In particular, women’s gains in executive power of a state and their rising representation in legislature are critical for legalizing same-sex marriages. The preeminent impact of expanding political power among women on advancing civil rights of same-sex couples reveals a vital aspect of social change that should be further explored in future research. 

Keywords: Same-sex civil union, same-sex marriage, economic development, INGO, civil society, women's political empowerment