Ralph David Abernathy Sr. (March 11, 1926 – April 17, 1990) was an American civil rights activist and Christian minister. As a leader of the nonviolent Civil Rights Movement, he was a close friend and mentor of Martin Luther King. He collaborated with King to create the Montgomery Improvement Association which led to the Montgomery Bus Boycott. He also co-founded and was an executive board member of the Southern Christian Leadership Conference (SCLC). He became president of the SCLC following the assassination of King in 1968, where he led the Poor People's Campaign in Washington, D. C. among other marches and demonstrations for disenfranchised Americans. He also served as an advisory committee member of the Congress on Racial Equality (CORE).