Mormons do not believe in the Trinity the same way that many Christians do, especially as it is written and interpreted in the Nicene Creed.

According to the Nicene Creed, God the Father, God the Son, and God the Holy Spirit are three coequal persons in the same substance or essence. This definition of God was written and refined in the first six ecumenical councils of Christianity. The first Council at Nicaea wrote the majority of the definition of God. This council was called by Emperor Constantine I after a large debate about the nature of God began threatening the unity of Christianity. 

Other denominations in Christianity vs. Mormonism: Mormons believe that God, the Eternal Father, His Son Jesus Christ, and the Holy Ghost are separate beings and they are divine. Mormons believe that all three are members of the Godhead and are united in purpose. However, they do not believe that the members of the Godhead are three coequal persons in the same substance, or essence, as defined by creeds and councils.