Martin Luther King Jr. was a prominent civil rights leader in the United States, known for his nonviolent activism against racial segregation and discrimination. His impact on civil rights is profound, as he advocated for equality through peaceful protests and powerful speeches, notably his "I Have a Dream" speech delivered during the 1963 March on Washington. King played a vital role in the advancement of the Civil Rights Movement, influencing legislation such as the Civil Rights Act and inspiring future generations to fight for social justice.