Coretta Scott King, known first as the wife of the Rev. Dr. Martin Luther King Jr., then as his widow, then as an avid proselytizer for his vision of racial peace and nonviolent social change, died early today at Santa Monica Hospital, in Baja California, Mexico, near San Diego. She was 78. Mrs. King was admitted to the hospital last Thursday, said her sister, Edythe Scott Bagley. She died about 1 a.m., said Lorena Blanco, a spokeswoman for the United States consulate in Tijuana.

In addition to dealing with her husband's death, which left her alone with four young children, Mrs. King faced other trials and controversies over the years. She was at times viewed as chilly and aloof by others in the movement. The King Center was criticized at first as competing for funds and siphoning energy from the Southern Christian Leadership Conference, which Dr. King had headed. In recent years, it has been widely viewed as adrift, characterized by intra-family squabbling and a focus more on Dr. King's legacy than on continuing his work. And even many allies were baffled and hurt by her campaign to exonerate James Earl Ray, who in 1969 pleaded guilty to her husband's murder, and her contention that Ray did not commit the crime. But more often, Mrs. King has been seen as an inspirational figure around the world, a tireless advocate for her husband's causes and a woman of enormous spiritual depth who came to personify the ideals Dr. King fought for.