There is one God. Father, Son, and Holy Spirit, a unity of three coeternal Persons. God is immortal, all powerful, all knowing, above all, and ever present. He is infinite and beyond human comprehension. He is forever worthy of worship, adoration, and service by the whole creation.

The Godhead

Scripture tells us that there is one God:

Hear, O Israel: The LORD our God is one LORD:
-Deuteronomy 6:4 (KJV)

Scripture also says that the Father is God.

But to us there is but one God, the Father, of whom are all things, and we in him; and one Lord Jesus Christ, by whom are all things, and we by him.
-1 Corinthians 8:6 (KJV)

Scripture also says that the Son/Christ is God

I and my Father are one.
-John 10:30 (KJV)

Scripture also says that the Holy Spirit is God.

And the earth was without form, and void; and darkness was upon the face of the deep. And the Spirit of God moved upon the face of the waters.
-Genesis 1:2 (KJV)

These Person's, the Father, the Son, and the Holy Spirit, constitute the Godhead.

Godhead- Old Testament

The divine summons in Genesis

And God said, Let us make man in our image, after our likeness: and let them have dominion over the fish of the sea, and over the fowl of the air, and over the cattle, and over all the earth, and over every creeping thing that creepeth upon the earth.
-Genesis 1:26 (KJV)

And the LORD God said, Behold, the man is become as one of us, to know good and evil: and now, lest he put forth his hand, and take also of the tree of life, and eat, and live forever:
-Genesis 3:22 (KJV)

This has often been understood to have the Godhead in view.

Isaiah 63 presents three divine Persons, the Father, Son, and Holy Spirit.

For he said, Surely they are my people, children that will not lie: so he was their Saviour.

Then he remembered the days of old, Moses, and his people, saying, Where is he that brought them up out of the sea with the shepherd of his flock? where is he that put his holy Spirit within him?

Doubtless thou art our father, though Abraham be ignorant of us, and Israel acknowledge us not: thou, O LORD, art our father, our redeemer; thy name is from everlasting.
-Isaiah 63:8,11,16 (KJV)

Godhead- New Testament

In the New Testament the Father, the Son, and the Holy Spirit are presented as distinct Persons, but as One God.

For there are three that bear record in heaven, the Father, the Word, and the Holy Ghost: and these three are one.
-1 John 5:7 (KJV)

Jesus prayed to the Father and asked for the Comforter (Holy Spirit) indicating three Persons functioning as One.

And I will pray the Father, and he shall give you another Comforter, that he may abide with you forever;
I will not leave you comfortless: I will come to you.
At that day ye shall know that I am in my Father, and ye in me, and I in you.
But the Comforter, which is the Holy Ghost, whom the Father will send in my name, he shall teach you all things, and bring all things to your remembrance, whatsoever I have said unto you.
-John 14:16,18,20,26 (KJV)

When Jesus was baptised in the River Jordon by John the Baptist, this is a clear picture of the Godhead, God speaking, Spirit of God descending like a dove (Holy Spirit), and Jesus coming up straightway out of the water.

And Jesus, when he was baptized, went up straightway out of the water: and, lo, the heavens were opened unto him, and he saw the Spirit of God descending like a dove, and lighting upon him:

And lo a voice from heaven, saying, This is my beloved Son, in whom I am well pleased.
-Matthew 3:16,17 (KJV)

Note below that the Baptism takes place not in the names, but in the name of the Father, the Son, and the Holy Spirit.

Go ye therefore, and teach all nations, baptizing them in the name of the Father, and of the Son, and of the Holy Ghost:
-Matthew 28:19 (KJV)

This implies that while the Persons of the Godhead are distinct, they are indissolubly united in essence and nature: Therefore it is evident that in God's substance there are three Persons, in which the One God is recognized.