The Porter–MacKenzie debate is a historiographical disagreement in the field of Modern British History about the importance of colonialism in 19th and 20th-century British culture. The debate was characterised by disagreement between the academic historians Bernard Porter and John MacKenzie. Porter argued that the expansion of empire during the era of New Imperialism had little effect on ordinary people in the United Kingdom, while the latter argued that colonialism dominated British popular culture for much of the period.