The internal slave trade in the United States, also known as the domestic slave trade, the Second Middle Passage and the interregional slave trade, involved the domestic trade of enslaved people within the United States that reallocated slaves across states during the Antebellum period. It was most significant after 1808, when the importation of slaves was prohibited. Historians estimate that one million slaves were taken in a forced migration from the Upper South, primarily Maryland and Virginia, to the territories and then new states of the Deep South: Georgia, Alabama, Florida, Louisiana, Mississippi, Arkansas, and Texas.

Economists say that transactions in the inter-regional slave market were driven primarily by differences in the marginal productivity of labor, which were based in the relative advantage between climates for the production of staple goods. The trade was strongly influenced by the invention of the cotton gin, which made short-staple cotton profitable for cultivation across large swathes of the upland Deep South (the Black Belt). Previously the commodity was based on long-staple cotton cultivated in coastal areas and the Sea Islands.

The disparity in productivity created arbitrage opportunities for traders to exploit, and it facilitated regional specialization in labor production. Due to a lack of data, particularly with regard to slave prices, land values, and export totals for slaves, the true effects of the domestic slave trade, on both the economy of the Old South and general migration patterns of slaves into southwest territories, remain uncertain. These have served as points of contention among economic historians.