Population transfer or resettlement is a type of mass migration, often imposed by state policy or international authority and most frequently on the basis of ethnicity or religion but also due to economic development. Banishment or exile is a similar process, but is forcibly applied to individuals and groups. Population transfer differs more than simply technically from individually motivated migration, but at times of war, the act of fleeing from danger or famine often blurs the differences. If a state can preserve the fiction that migrations are the result of innumerable "personal" decisions, the state may be able to claim that it is not to blame for the displacement.

Often the affected population is transferred by force to a distant region, perhaps not suited to their way of life, causing them substantial harm. In addition, the process implies the loss of immovable property and substantial amounts of movable property when rushed. This transfer may be motivated by the more powerful party's desire to make other uses of the land in question or, less often, by disastrous environmental or economic conditions that require relocation.

The first known population transfers date back to Ancient Assyria in the 13th century BCE, with forced resettlement being particularly prevalent during the Neo-Assyrian Empire. The single largest population transfer in history was the Partition of India in 1947 that involved up to 12 million people in Punjab Province with a total of up to 20 million people across British India, with the second largest being the flight and expulsion of Germans after World War II, which involved more than 12 million people.

Prior to the forcible deportation of Ukrainians (including thousands of children) to Russia during the 2022 Russian invasion of Ukraine, the last major population transfer in Europe was the deportation of 800,000 ethnic Albanians during the Kosovo War in 1999. Moreover, some of the largest population transfers in Europe have been attributed to the ethnic policies of the Soviet Union under Joseph Stalin. The best-known recent example caused by economic development is that resulting from the construction of the Three Gorges Dam in China.