While acknowledging many ‘Gods’ or celestial beings, Sanatan Dharma actually believes in one supreme God who creates and sustains the universe. The word God in itself suggests that He is unique and is Supreme, supreme as in the greatest and no one greater. Logically there cannot be more than one Supreme Being. If ones greatness was equal to another’s greatness then neither would be supreme. Therefore the word ‘Gods’ is grammatically incorrect. According to the Vedic scriptures, there are numerous Hindu deities that serve as “Manifestations” of this “One Supreme God”.
In Bhagavat Gita Lord Talks about himself but what he is referring to throughout is that One Supreme God. And he tells us in details about this Supreme Being. This part has been dealt with in details by the Lord in Chapter 10. From Verse 21 to Verse 40 he tells in details all where He is present making it clear God is omnipresent. Here are few shlokas where he makes it clear that God is none but that One Supreme Being!
yo mam ajam anadim ca vetti loka-mahesvaram,
asammudhah sa martyesu sarva-papaih pramucyate.
He who knows Me as the Unborn One without a beginning and also knows Me as the great Lord of the world, is not deluded among mortals and is delivered from all reactions to sin.
aham atma gudakesa sarva-bhutasaya-sthitah,
aham adis ca madhyam ca bhutanam anta eva ca.
I am, O Arjuna, the soul in the heart of all living beings; I am the origin, also the middle and as well indeed the end of all existing.
sarganam adir antas ca madhyam caivaham arjuna,
adhyatma-vidya vidyanam vadah pravadatam aham.
Of all creations I am the beginning and the end and also the middle, O Arjuna. Of all sciences I am the spiritual science of the Self, and among logicians I am the conclusive truth.
yac capi sarva-bhutanam bijam tad aham arjuna,
na tad asti vina yat syan maya bhutam caracaram.
O Arjuna, I am the generating seed of all existences. Of whatever that of all the beings may exist I am the source; nothing of the moving and unmoving exists without Me.
nanto 'sti mama divyanam vibhutinam parantapa,
esa tuddesatah prokto vibhuter vistaro maya.
O mighty conqueror of enemies, there is no end to My divine manifestations. What I have spoken to you is but a mere indication of My infinite opulence’s.
yad yad vibhutimat sattvam srimad urjitam eva va,
tat tad evavagaccha tvam mama tejo-'msa-sambhavam,
Whatever of power that has existence and is of beauty and glory indeed, all those you must certainly know as being born as a part of My splendor.