Immigration to Europe has a long history, but increased substantially after World War II. Western European countries, especially, saw high growth in immigration post 1945, and many European nations today (particularly those of the EU-15) have sizeable immigrant populations, both of European and non-European origin. In contemporary globalization, migrations to Europe have accelerated in speed and scale. Over the last decades, there has been an increase in negative attitudes towards immigration, and many studies have emphasized marked differences in the strength of anti-immigrant attitudes among European countries.

Beginning in 2004, the European Union granted EU citizens freedom of movement and residence within the EU, and the term "immigrant" has since been used to refer to non-EU citizens, meaning that EU citizens are not to be defined as immigrants within EU territory. The European Commission defines "immigration" as the action by which a person from a non-EU country establishes his or her usual residence in the territory of an EU country for a period that is or is expected to be at least twelve months. Between 2010 and 2013, around 1.4 million non-EU nationals, excluding asylum seekers and refugees, immigrated into the EU each year using regular means, with a slight decrease since 2010.

Historical migration into or within Europe has mostly taken the form of military invasion, but there have been exceptions; this concerns notably population movements within the Roman Empire under the Pax Romana; the Jewish diaspora in Europe was the result of the First Jewish–Roman War of AD 66–73.

With the collapse of the Roman Empire, migration was again mostly coupled with warlike invasion, not least during the so-called migration period (Germanic), the Slavic migrations, the Hungarian conquest of the Carpathian Basin, the Islamic conquests and the Turkic expansion into Eastern Europe (Kipchaks, Tatars, Cumans). The Ottomans once again established a multi-ethnic imperial structure across Western Asia and Southeastern Europe, but Turkification in Southeastern Europe was due more to cultural assimilation than to mass immigration. In the late medieval period, the Romani people moved into Europe both via Anatolia and the Maghreb.

There were substantial population movements within Europe throughout the Early Modern period, mostly in the context of the Reformation and the European wars of religion, and again as a result of World War II.

From the late 15th century until the late 1960s and early 1970s, Greece, Ireland, Italy, Germany, Norway, Sweden, Denmark, Belgium, Portugal, Spain and the United Kingdom were primarily sources of emigration, sending large numbers of emigrants to the Americas, Australia, Siberia and Southern Africa. A number also went to other European countries (notably France, Switzerland, Germany and Belgium). As living standards in these countries have risen, the trend has reversed and they were a magnet for immigration (most notably from Morocco, Somalia, Egypt to Italy and Greece; from Morocco, Algeria and the Americas to Spain and Portugal; and from Ireland, India, Pakistan, Germany, the United States, Bangladesh, and Jamaica to the United Kingdom).

Article 17 of the Schengen Agreement aims at moving internal borders to external borders.

Mobility or mobility of workers is the name given to ease people from one EU country to work into another EU country. The Maastricht treaty name it "the free movement of persons". This is one of the key principles of the European Union.