The Great Migration, sometimes known as the Great Northward Migration or the Black Migration, was the movement of six million African Americans out of the rural Southern United States to the urban Northeast, Midwest, and West between 1910 and 1970. It was substantially caused by poor economic and social conditions due to prevalent racial segregation and discrimination in the Southern states where Jim Crow laws were upheld. In particular, continued lynchings motivated a portion of the migrants, as African Americans searched for social reprieve. The historic change brought by the migration was amplified because the migrants, for the most part, moved to the then-largest cities in the United States (New York City, Chicago, Detroit, Los Angeles, San Francisco, Philadelphia, Cleveland, and Washington, D.C.) at a time when those cities had a central cultural, social, political, and economic influence over the United States; there, African Americans established culturally influential communities of their own.[4] According to Isabel Wilkerson, despite the losses they felt leaving their homes in the South, and despite the barriers which the migrants faced in their new homes, the migration was an act of individual and collective agency, which changed the course of American history, a "declaration of independence" which was written by their actions.

From the earliest U.S. population statistics in 1780 until 1910, more than 90% of the African-American population lived in the American South, making up the majority of the population in three Southern states, namely Louisiana (until about 1890), South Carolina (until the 1920s), and Mississippi (until the 1930s). But by the end of the Great Migration, just over half of the African-American population lived in the South, while a little less than half lived in the North and West. Moreover, the African-American population had become highly urbanized. In 1900, only one-fifth of African Americans in the South were living in urban areas. By 1960, half of the African Americans in the South lived in urban areas,  and by 1970, more than 80% of African Americans nationwide lived in cities.

Some historians analyze the Great Migration in two parts, a first Great Migration (1910–40), during which about 1.6 million people moved from mostly rural areas in the South to northern industrial cities, and a Second Great Migration (1940–70), which began after the Great Depression and during it, at least five million people—including townspeople with urban skills—moved to the North and West.

Since the Civil Rights Movement, the trend has reversed, with more African Americans moving to the South, albeit far more slowly. Dubbed the New Great Migration, these moves were generally spurred by the economic difficulties of cities in the Northeastern and Midwestern United States, growth of jobs in the "New South" and its lower cost of living, family and kinship ties, and lessening discrimination.