Soon after the collapse of Soviet-type communism in Central and Eastern Europe, a new geopolitical division began to reshape the continent. Our study demonstrates that this newly emerging geopolitical divide has been underpinned by a corresponding cultural divergence, of which “emancipative values” are the most powerful marker. Using the European Values Study/World Values Survey 1990 to 2014, we find that the former Iron Curtain no longer constitutes a cultural boundary because the ex-communist states that joined the European Union have been converging with the West’s strong emphasis on emancipative values. Instead, a new and steeply growing cultural gap has emerged between the European Union and its Eastern neighbors. The two competing geopolitical formations in the West and East—the European and Eurasian Unions, respectively—have diverged culturally in recent decades. The divergence goes back to contrasting supranational identities that originate in different religious traditions, which rulers have increasingly accentuated to strengthen their nations’ endorsement or dismissal of emancipative values. Through this sorting-out process, emancipative values became an increasingly significant marker of a Western-vs-Eastern cultural identity. Our study is the first to link this groundbreaking cultural transformation to civilizational identities and geopolitical rivalry.