Bahá’ís believe there is one God, who is beyond human understanding.  We can only know God through His Manifestations.

Bahá’u’lláh wrote:

“Regard thou the one true God as One Who is apart from, and immeasurably exalted above, all created things. The whole universe reflecteth His glory, while He is Himself independent of, and transcendeth His creatures…”
(Gleanings from the Writings of Bahá’u’lláh, p. 166)

“To every discerning and illuminated heart it is evident that God, the unknowable Essence, the Divine Being, is immensely exalted beyond every human attribute, such as corporeal existence, ascent and descent, egress and regress. Far be it from His glory that human tongue should adequately recount His praise, or that human heart comprehend His fathomless mystery. He is, and hath ever been, veiled in the ancient eternity of His Essence, and will remain in His Reality everlastingly hidden from the sight of men…”
(Gleanings from the Writings of Bahá’u’lláh, p. 46-47)

“…The door of the knowledge of the Ancient Being hath ever been, and will continue for ever to be, closed in the face of men. No man’s understanding shall ever gain access unto His holy court. As a token of His mercy, however, and as a proof of His loving-kindness, He hath manifested unto men the Day Stars of His divine guidance, the Symbols of His divine unity, and hath ordained the knowledge of these sanctified Beings to be identical with the knowledge of His own Self. Whoso recognizeth them hath recognized God. Whoso hearkeneth to their call, hath hearkened to the Voice of God, and whoso testifieth to the truth of their Revelation, hath testified to the truth of God Himself. Whoso turneth away from them, hath turned away from God, and whoso disbelieveth in them, hath disbelieved in God. Every one of them is the Way of God that connecteth this world with the realms above, and the Standard of His Truth unto every one  in the kingdoms of earth and heaven. They are the Manifestations of God amidst men, the evidences of His Truth, and the signs of His glory.”
(Gleanings from the Writings of Bahá’u’lláh, p. 49-50)