Colonialism broadly refers to the practice by which one polity exerts control over territory and populations beyond its own borders, often to extract resources, settle people, or extend strategic influence. Early forms of expansion that resemble colonial control appear in many eras and places: ancient states and civilizations sometimes established dependencies, trading outposts or governed distant provinces. For discussions of the concept in modern scholarship see colonialism.

Early examples and distinctions

Long before the maritime empires of Europe, a range of societies engaged in actions that historians discuss in terms of imperial rule or colonization. The Hittites, for instance, established control over neighboring regions and client states (Hittites), while continental powers like the Persian and Roman polities extended provincial systems and settler layers (Roman Empire). Scholars often distinguish overland empires—frequently labeled imperialism—from overseas colonial systems. Examples of expansive continental polities include the Mongol Empire, which spanned from parts of the Western Pacific to Eastern Europe, the campaigns of Alexander the Great, and the early Islamic dominions such as the Umayyad Caliphate. Byzantine institutions and later the Ottoman state also combined administrative control and cultural influence in large territories (Byzantine Empire, Ottoman Empire).

European overseas expansion (15th–18th centuries)

The phase most often meant by modern discussions of colonialism began in the fifteenth century, when Iberian kingdoms sponsored voyages to new maritime routes. Spanish and Portuguese voyages opened direct contact with the Americas and coastal regions of Africa and Asia (Spanish, Portuguese). These voyages established trading posts, settler colonies and systems of resource extraction across the coasts of Africa, the Middle East, India and parts of East Asia. Over the next two centuries other European states—England, France and the Dutch Republic—built their own overseas networks (England, France, Holland), establishing colonies in the Americas, Africa and Asia and creating long-distance trade circuits.

19th‑century expansion and the so‑called New Imperialism

After independence movements in the Americas reduced Iberian dominance, 19th-century Europe underwent industrial, military and demographic transformations that made new forms of territorial expansion possible. Britain (Britain), France and other powers directed imperial ambitions toward regions such as South Africa, the Indian subcontinent (India) and Southeast Asia. This era—sometimes called the era of New Imperialism—saw fast territorial acquisitions, commercial colonization and intense competition, culminating in events like the Scramble for Africa. Rivalries over colonies were factors in the tensions that contributed to World War I.

Decolonization and the 20th century

The two world wars reshaped international power and accelerated decolonization. Following World War I, some territories changed hands as defeated empires relinquished overseas possessions; after World War II a broad wave of independence movements, diplomatic pressure and changing global norms led most colonies to become sovereign states. European control over non-European territories waned across mid-20th century Asia and Africa; the transfer of Macau from Portugal back to the People’s Republic of China in 1999 is often cited as one of the last formal acts closing the long span of European overseas colonial administration (World War II and its aftermath were key turning points).

Characteristics, legacy and debate

Colonial systems varied widely: settler colonies imported large numbers of migrants and often displaced indigenous populations; trading empires relied on fortified ports and mercantile networks; direct-rule colonies imposed metropolitan institutions, while indirect-rule systems worked through local elites. The legacies of colonialism include altered economic patterns, linguistic and legal influences, demographic change, and contested memory. Historians and communities debate responsibility, restitution and how to understand long-term effects on development, governance and identity.