This dissertation sheds new light on the Purātan Janamsākhī, the earliest available account on the founder and most important figure of the Sikh tradition – Gurū Nānak (d. 1539 CE). Scholarship on Gurū Nānak has largely dismissed the significance of this text and has overlooked the fact that, after its composition in 1588 CE, the Purātan Janamsākhī remained the most widely circulated account of Gurū Nānak’s life for two centuries. This thesis engages with the manuscripts and studies of the text to provide a life-history of the Purātan Janamsākhī, and, in arguing for a reclamation of this account, takes on a close reading of the Purātan Janamsākhī to identify how, within decades of his death, followers of Gurū Nānak remembered his life and message. This thesis situates the Purātan Janamsākhī within its historical context and compares it with some of its closest North Indian contemporaries, including other janamsākhīs composed on the life of Gurū Nānak and hagiographical writings written about religious figures from different North Indian communities. Our comparative approach allows us to identify some basic commonalities in hagiographical writing and glean aspects that distinguish the Purātan Janamsākhī from its counterparts, including Gurū Nānak’s unique interest in political critique and building a new community. This thesis, therefore, contributes significantly to our understandings of identity and community formation, to studies on hagiographical writing, and to our foundational understandings of Sikh history.