The First Council of Nicaea, convened by Emperor Constantine in the year 325 AD, was a landmark ecumenical council that brought together Christian bishops to resolve theological disputes concerning the nature of Jesus Christ. Its primary achievement was formulating the original Nicene Creed, which affirmed that Jesus is of the same substance as the Father, thereby rejecting the Arian view that Christ was a created being. This pivotal gathering established a unified orthodox doctrine regarding the divinity of Christ and set a precedent for future ecumenical councils in defining core Christian beliefs.