The famous civil rights activist known for his role in the Montgomery Bus Boycott is Rosa Parks. On December 1, 1955, in Montgomery, Alabama, Parks refused to give up her seat to a white passenger on a segregated bus, leading to her arrest. Her brave act of defiance became a catalyst for the Montgomery Bus Boycott, which lasted over a year and aimed to end racial segregation in public transportation. Parks worked alongside other key figures, including Martin Luther King Jr., and her contribution significantly advanced the civil rights movement in the United States. She is often celebrated as "the mother of the civil rights movement."