The South Atlantic Co-Dominion, sometimes simply known as the Co-Dominion, is a series of widely scattered islands in the South Atlantic: the Falklands, South Georgia, the South Sandwich Islands, the South Orkneys and the South Shetlands, administered jointly by the governments of Argentina and the Federated Kingdom of Great Britain and the Islands. It also makes some joint claims of territory in Antarctica. It was set up on 1st January, 1975 after the UK complied with UN Resolution 3160 to enter negotiations with Argentina on the sovereignty of the islands, thereby avoiding possible conflict, largely over possible nearby oil reserves. The arrangement is similar to the previous arrangement between the UK and China regarding Hong Kong in that there is a ninety-nine year term for the agreement, but different in that there is joint "ownership" of the territory. Since the advent of readily available solar power sources, the matter of oil has become irrelevant.

There has been some criticism that the British have never used this situation to bring pressure upon the Argentine government to improve their human rights record. When questioned on this matter, the government have tended to respond that their very presence is likely to have ameliorated the situation in Argentina.