The aim of this chapter is to systematically examine early migration theories and to understand the phenomenon of migration through these approaches. Migration, as old as human history, is a multi-dimensional social process that refers to individuals and communities leaving their place of residence and settling elsewhere temporarily or permanently due to economic, political, social, environmental, and cultural reasons. In this respect, migration is not only spatial mobility but also a dynamic phenomenon that transforms social structures, economic relations, political balances, and cultural interactions. Early theories developed to explain the phenomenon of migration are examined within the framework of five main approaches. First, Ravenstein's Migration Theory is considered the first systematic theoretical effort to explain migration in terms of certain regularities and "laws"; it particularly emphasizes the effects of industrialization and urbanization on migration. Second, Marxist theory examines migration within the context of capitalist production relations, class structure, and global inequalities; it links international migration to center-periphery relations and the structural needs of labor markets. The third approach, Stouffer's Intersecting Opportunities Theory, explains migration decisions not through distance but through the number and quality of opportunities individuals encounter along the way; it focuses on the micro-level dynamics of migration. Fourthly, Lee's Push-Pull Theory, which he systematized, considers migration as a multidimensional process within the framework of push and pull factors in source and destination regions and the obstacles in the migration process. Finally, Petersen's Classification of Migration reveals the heterogeneous nature of the migration phenomenon by categorizing migration into five types—primitive, forced, directed, free, and mass migration—according to levels of individual will and historical-social conditions. In general, it reveals the efforts of early migration theories to explain the causes and forms of migration at different levels. By discussing the contributions and limitations of each approach, it emphasizes the multidimensional and dynamic nature of the migration phenomenon.