The Great Replacement, also known as replacement theory or great replacement theory, is a white nationalist far-right conspiracy theory espoused by French author Renaud Camus. The original theory states that, with the complicity or cooperation of "replacist" elites, the ethnic French and white European populations at large are being demographically and culturally replaced by non-white peoples—especially from Muslim-majority countries—through mass migration, demographic growth and a drop in the birth rate of white Europeans. Since then, similar claims have been advanced in other national contexts, notably in the United States. Mainstream scholars have dismissed these claims of a conspiracy of "replacist" elites as rooted in a misunderstanding of demographic statistics and premised upon an unscientific, racist worldview. According to the Encyclopædia Britannica, the Great Replacement "has been widely ridiculed for its blatant absurdity."

During 2015, there was a period of significantly increased movement of refugees and migrants into Europe. 1.3 million people came to the continent to request asylum, the most in a single year since World War II. They were mostly Syrians, but also included significant numbers from Afghanistan, Nigeria, Pakistan, Iraq, Eritrea, and the Balkans. The increase in asylum seekers has been attributed to factors such as the escalation of various wars in the Middle East and ISIL's territorial and military dominance in the region due to the Arab Winter, as well as Lebanon, Jordan, and Egypt ceasing to accept Syrian asylum seekers.