The Holy Spirit is a part of what is known as the Holy Trinity in the Christian belief . For the majority of Christians the Holy Spirit ( prior English language usage : the Holy Ghost ( from Old English gast , â spiritâ ) is the third person of the Holy Trinityâ '' Father , Son , and Holy Spirit , and is Almighty God . The Holy Spirit is seen by mainstream Trinitarian Christians as one Person of the Triune God , who revealed His Holy Name YHWH to his people Israel , sent His Eternally Begotten Son Jesus to save them , and sent the Holy Spirit to Sanctify and give Life to his Church .