Who is the narrator of Conrad's novel that involves a boat trip up the Congo River to Inner Station?

Charles Marlow-

Heart of Darkness (1899) is a novella by Polish-English novelist Joseph Conrad about a narrated voyage up the Congo River into the Congo Free State in the so-called heart of Africa. Charles Marlow, the narrator, tells his story to friends aboard a boat anchored on the River Thames.

The novel that this refers to is Heart of Darkness by Joseph Conrad. This novel was written between 1898 and 1899 in England, based on the experiences that Conrad had had in Africa. In this novel, we find two narrators that coexist. First, there is an anonymous passenger on a pleasure ship who is listening to Marlow's story. The second one is Charles Marlow himself, who is a middle-aged ship's captain.