The notable event that led Nelson Mandela to become an international symbol of resistance to apartheid was his imprisonment for 27 years. Initially charged with treason for opposing racial segregation and injustice in South Africa, Mandela's imprisonment drew global attention to the anti-apartheid movement. His release in 1990 signified hope for reform, and he became a leader in negotiating the end of apartheid, embodying the struggle for freedom and equality that inspired millions worldwide.