Colonialism is a game of 19th Century imperialistic struggle. In this game, each player assumes the role of a nondescript colonial power. Players proceed to struggle for influence in the unindustrialized regions of the world, and the subsequent resources such influence entails.

Each turn is divided into action phases and colonization phases. During action phases, players use cards to secretly bid influence in the six regions of the game board. During colonization phases, all cards in play are revealed, the placement of influence is resolved, and conflict occurs.

Whenever all native influence is eliminated from a region, that region's resources are collected. The amount of resources collected by each player depends on each players' influence in the region. At the end of the game, the player who collects the most resources wins.