Shri Guru Nanak is the founder of Sikhism. Sikhism is still based on his teachings and. Those of the nine Sikh Gurus who followed him. Guru Nanak Gurpurab also known as Guru. Nanak Dev Ji's Prakash Utsav, marks the birth anniversary of the first Sikh Guru, Guru. Nanak. This is one of the most sacred festivals in Sikhism. Apart from Sikhs, the.