The end of the Napoleonic Wars brought new additions to the British colonial empire. It was replenished with possessions in Europe, including the Ionian Islands, which had experience of their own statehood: at the end of the 18th – beginning of the 19th centuries, there existed an autonomous Septinsular Republic under the supreme authority of the Ottoman Sultan and a protectorate of Russia. Historians disagree on how to characterize British rule on the islands: in Greece it is often called colonial, while the Anglo-American tradition has softer assessments. This article analyzes the protectorate regime established by Great Britain on the islands (1815–1864) and discusses whether it can be considered colonial. On this purpose, we examine the conditions under which Great Britain obtained a protectorate over the archipelago; study the fundamental documents on which it was founded; give an overview of the policies of the Lords High Commissioners of the island state and its political development; and analyze the attitude of the local population to British rule.