What mental illness was Riel believed to be suffering from?

Louis Riel was often thought to have been suffering from megalomania, particularly during his time as a leader in the Red River and North-West Rebellions. Megalomania is characterized by an obsession with power, often manifesting as an inflated sense of self-importance and a delusion of grandeur. Riel's belief that he was a divinely chosen leader for the Métis people and his perception of his own role in the larger national context reflect the traits associated with this condition.

Historical accounts indicate that Riel displayed behaviors and ideas that align with megalomania, particularly as he became more embroiled in political and social issues affecting the Métis community. His strong conviction in his mission and his vision for the Métis rights and sovereignty led him to take extreme actions which, seen through a modern psychological lens, could be interpreted as symptoms of this mental illness.

Although some might consider other mental health diagnoses based on Riel's behaviors, megalomania specifically captures the aspect of grandiosity and perceived superiority that characterized his leadership style and self-identity during critical moments in his life.