The prominent abolitionist and former slave who wrote "Narrative of the Life of Frederick Douglass" is Frederick Douglass. His autobiography is a pivotal work in American literature and provides a first-hand account of his experiences with slavery, escape, and eventual advocacy for abolition. Douglass's eloquent writing and speeches were instrumental in the anti-slavery movement and raised awareness about the brutal realities of enslavement. His life story remains a testament to the strength and resilience of those who fought for freedom and equal rights.