Which council condemned Nestorius's teachings?

The Third Ecumenical Council, held in Ephesus in 431 AD, is the council that condemned the teachings of Nestorius. Nestorius was the Patriarch of Constantinople who proposed a Christological doctrine that emphasized a distinction between the divine and human natures of Christ to the extent that some viewed it as suggesting there were two separate persons in Christ. This view contradicted the more widely accepted belief in the hypostatic union, where Christ is understood to have both a fully divine and fully human nature in one person.

The council was significant in affirming the title "Theotokos," meaning "God-bearer" or "Mother of God," for the Virgin Mary, countering Nestorius's assertion that Mary should be called "Christotokos," or "Christ-bearer," which indicated a division in Christ’s nature. The decisions made at this council helped define the orthodox Christian understanding of the nature of Christ and solidify the church's stance against Nestorianism, leading to his eventual condemnation.

Understanding this context is essential as it illustrates the pivotal role that the Third Ecumenical Council played in shaping early Christian doctrine, specifically regarding the nature of Christ and the legitimacy of Marian titles.