The civil rights activist known for their significant role in the fight against racial segregation is Rosa Parks. Her courageous refusal to give up her bus seat to a white passenger in Montgomery, Alabama, in 1955 sparked the Montgomery Bus Boycott and became a catalyst for the civil rights movement. Parks’s act of defiance symbolized the struggle against racial injustice and inspired others to take action. Her legacy is deeply woven into American history, illustrating the power of individual resistance in the pursuit of social change and equality.