Firm migration is a very important determinant of regional economic dynamics. This entry gives an overview of the present state of the theories and empirical findings on this topic. The spatial scale is important, because the causes and effects differ substantially for firm relocations within urban areas and between regions within countries, and for international relocations between countries or even continents. Firm migration research started in the 1950s and 1960s by studying the relocation of manufacturing firms in the context of regional development policies. Early on firm‐external factors were the main explanatory factors, but later on the role of firm‐internal factors and the phases in the decision‐making process became more important as better data and methods were available.