In Sikhism, God is conceived as the Oneness that permeates the entirety of creation and beyond. It abides within all of creation as symbolized by the symbol Ik Onkar. The One is indescribable yet knowable and perceivable to anyone who surrenders their egoism and meditates upon that Oneness. The Sikh gurus have described God in numerous ways in their hymns included in the Guru Granth Sahib, the holy scripture of Sikhism, but the oneness of formless God is consistently emphasized throughout.

God is described in the Mul Mantar (lit. the Prime Utterance), the first passage in the Guru Granth Sahib:

ੴ ਸਤਿ ਨਾਮੁ ਕਰਤਾ ਪੁਰਖੁ ਨਿਰਭਉ ਨਿਰਵੈਰੁ ਅਕਾਲ ਮੂਰਤਿ ਅਜੂਨੀ ਸੈਭੰ ਗੁਰ ਪ੍ਰਸਾਦਿ ॥
ikk ōankār sat(i)-nām(u) karatā purakh(u) nirabha'u niravair(u) akāla mūrat(i) ajūnī saibhan(g) gur(a) prasād(i).
There is only one God, and It is called the truth, It exists in all creation, and It has no fear, It does not hate, and It is timeless, universal and self-existent! You will come to know it through the grace of the Guru.

— Sri Guru Granth Sahib, page 1

Sikhi is monotheistic and believes that there is only One God. Guru Nanak, the founder of Sikhi strongly denounces any type of Pakhand (hypocrisy or duality). Nanak prefixed the numeral "IK" (one) to the syllable Onkar to stress the idea of God's oneness; that the Creator, Preserver, and Destroyer is One. Sikh thought begins with the One Almighty and then universalising God, coming down to the cosmic reality of all-pervading creator. While God is described as without gender, God is also described through numerous metaphors, such as:

ਏਕੁ ਪਿਤਾ ਏਕਸ ਕੇ ਹਮ ਬਾਰਿਕ ਤੂ ਮੇਰਾ ਗੁਰ ਹਾਈ ॥

"Ek(u) pitaa ekas ke ham baarik"

"The One God is the Father of all;