Human migration is the movement of people from one place to another, with intentions of settling, permanently or temporarily, at a new location (geographic region). The movement often occurs over long distances and from one country to another (external migration), but internal migration (within a single country) is the dominant form of human migration globally.

Migration is often associated with better human capital at both individual and household level, and with better access to migration networks, facilitating a possible second move. It has a high potential to improve human development, and some studies confirm that migration is the most direct route out of poverty. Age is also important for both work and non-work migration. People may migrate as individuals, in family units or in large groups. There are four major forms of migration: invasion, conquest, colonization and emigration/immigration.

People moving from their home due to forced displacement (such as a natural disaster or civil disturbance) may be described as displaced persons or, if remaining in the home country, internally-displaced persons. People who flee to a different country due to political, religious, or other types of persecution in their home country can formally request shelter in the host country. These people are commonly referred to as asylum seekers. If the application is approved, their legal classification changes to that of refugees.

Depending on the goal and reason for relocation, migrants can be divided into three categories: migrants, refugees, and asylum seekers. Each category is defined broadly as the combination of circumstances that motivate a person to change their location. As such, migrants are traditionally described as persons who change the country of residence for general reasons. These purposes may include better job opportunities or healthcare needs. This term is the most widely understood, as anyone changing their geographical location permanently is a migrant.

In contrast, refugees are defined by the UNHCR as "persons forced to flee their country because of violence or persecution". The reasons for the refugees' migration usually involve war actions within the country or other forms of oppression, coming either from the government or non-governmental sources. Refugees are usually associated with people who must unwillingly relocate as fast as possible; hence, such migrants are likely to relocate undocumented.

Asylum seekers are associated with persons who also leave their country unwillingly, yet, who also do not do so under oppressing circumstances such as war or death threats. The motivation to leave the country for asylum seekers might involve an unstable economic or political situation or high rates of crime. Thus, asylum seekers relocate predominantly to escape the degradation of the quality of their lives.

Nomadic movements usually are not regarded as migrations, as the movement is generally seasonal, there is no intention to settle in the new place, and only a few people have retained this form of lifestyle in modern times. Temporary movement for travel, tourism, pilgrimages, or the commute is also not regarded as migration, in the absence of an intention to live and settle in the visited places.

There exist many statistical estimates of worldwide migration patterns. The World Bank has published three editions of its Migration and Remittances Factbook, beginning in 2008, with a second edition appearing in 2011 and a third in 2016. The International Organisation for Migration (IOM) has published ten editions of the World Migration Report since 1999. The United Nations Statistics Division also keeps a database on worldwide migration. Recent advances in research on migration via the Internet promise better understanding of migration patterns and migration motives.