Who is the Big Man and the President in A Bend in The River? Are they the same person? What are their roles?

The Big Man and the President are the same person in V. S. Naipaul's A Bend in the River; "The Big Man" is just a more colloquial, casual phrase that people use to refer to the President.

In this novel, which explores postcolonial identity crisis and the circular crisis of exile, The Big Man becomes the President of Africa after Africa achieves independence. In order to rebuild Africa after years of having suffered under European colonial influences, the President drives out all non-African residents and orders that their structural creations be vandalized; this effort is intended "to wipe out the memory of the intruder." In reality, these actions cause Africa to suffer even more.

The President/The Big Man is an unstable leader for the country and has little trust in those who surround him, discarding his advisors or staff when they cease to be of use--or even worse, appear to be a threat. He eventually implements policies of radicalization, which force the main characters of the novel (including Salim) to ironically flee to the land of those who first colonized Africa in search of civilization and sanctuary: that is to say, Europe.