A colonizer is a person or country that takes control of another land and its people, often by force, to settle there and extract resources. Throughout history, powerful nations sent colonizers to distant territories to claim land, establish settlements, and impose their own laws and customs on the people already living there.

When European countries like Spain, England, and France sent colonizers to the Americas, Africa, and Asia starting in the 1500s, these newcomers often treated the indigenous peoples unfairly, taking their land and resources while disregarding their rights and cultures. Spanish colonizers who arrived in Mexico and South America, for example, conquered the Aztec and Inca empires. British colonizers established settlements along the eastern coast of North America, which eventually became the thirteen colonies that formed the United States.

While ancient Romans established colonies throughout Europe, the term colonizer today often carries negative weight because of how colonizing powers treated the people whose lands they took. The process of colonization caused enormous suffering for indigenous populations through disease, displacement, and oppression.

When countries finally gained independence from their colonizers, like when India freed itself from British rule in 1947 or when many African nations won independence in the 1960s, they could govern themselves again.