Gurū Nānak (15 April 1469 – 22 September 1539; Gurmukhi: ਗੁਰੂ ਨਾਨਕ), also known as Bābā Nānak ('Father Nanak'), was an Indian spiritual teacher, mystic and poet, who is regarded as the founder of Sikhism and is the first of the ten Sikh Gurus.
Nanak is said to have travelled far and wide across Asia teaching people the message of Ik Onkar (ੴ, 'One God'), who dwells in every one of his creations and constitutes the eternal Truth. With this concept, he would set up a unique spiritual, social, and political platform based on equality, fraternal love, goodness, and virtue.
Nanak's words are registered in the form of 974 poetic hymns, or shabda, in the holy religious scripture of Sikhism, the Guru Granth Sahib, with some of the major prayers being the Japji Sahib (jap, 'to recite'; ji and sahib are suffixes signifying respect); the Asa di Var ('Ballad of Hope'); and the Sidh Gosht ('Discussion with the Siddhas'). It is part of Sikh religious belief that the spirit of Nanak's sanctity, divinity, and religious authority had descended upon each of the nine subsequent Gurus when the Guruship was devolved on to them. His birthday is celebrated as Guru Nanak Gurpurab, annually across India.