उपनिवेश (कालोनी) किसी राज्य के बाहर की उस दूरस्थ बस्ती को कहते हैं जहाँ उस राज्य की जनता निवास करती है। किसी पूर्ण प्रभुसत्ता संपन्न राज्य के लोगों के अन्य देश की सीमा में जाकर बसने के स्थान के लिए भी इस शब्द का प्रयोग होता है।

A colony is a territory subject to a form of foreign rule. Though dominated by the foreign colonizers, the rule remains separate to the original country of the colonizers, the metropolitan state, which together have often been organized as colonial empires, particularly with the development of modern imperialism and its colonialism. This coloniality and possibly colonial administrative separation, while often blurred, makes colonies neither annexed or integrated territories nor client states. Colonies contemporarily are identified and organized as not sufficiently self-governed dependent territories. Other past colonies have become either sufficiently incorporated and self-governed, or independent, with some to a varying degree dominated by remaining colonial settler societies or neocolonialism.