The civil rights activist known for boycotting racial segregation is Rosa Parks. On December 1, 1955, in Montgomery, Alabama, Parks famously refused to give up her seat on a segregated bus to a white passenger, leading to her arrest. This courageous act of defiance became a pivotal moment in the American civil rights movement, sparking the Montgomery Bus Boycott. The boycott lasted over a year and ultimately led to a Supreme Court ruling that declared segregation on public buses unconstitutional. Parks' actions and the subsequent boycott galvanized the movement, exemplifying the struggle for racial equality in the United States.