The Church - instituted by Christ Jesus
It was the Son's task to accomplish the Father's plan of salvation in the fullness of time. Its accomplishment was the reason for his being sent. "The Lord Jesus inaugurated his Church by preaching the Good News, that is, the coming of the Reign of God, promised over the ages in the scriptures." To fulfill the Father's will, Christ ushered in the Kingdom of heaven on earth. The Church "is the Reign of Christ already present in mystery."
Source: Catechism of the Catholic Church (Vatican.va)