Theotokos — God-bearer — is not a Marian superlative. It is a Christological entailment. This article traces the title from its biblical spine in Galatians 4:4 and Luke 1, through the Ark of the Covenant typology, Irenaeus's New Eve theology, and the drama of Ephesus (AD 431), to Lumen Gentium's definitive treatment. Every source verified. Every claim grounded.