What's the official name of the island country lying southeast of the Federated States of Micronesia?
Nauru ( nah-OO-roo or  NOW-roo; Nauruan: Naoero), officially the Republic of Nauru (Nauruan: Repubrikin Naoero) and formerly known as Pleasant Island, is an island country in Micronesia, a subregion of Oceania, in the Central Pacific. Its nearest neighbour is Banaba Island in Kiribati, 300 kilometres (190 mi) to the east. It further lies northwest of Tuvalu, north of the Solomon Islands, east-northeast of Papua New Guinea, southeast of the Federated States of Micronesia and south of the Marshall Islands. With only a 21-square-kilometre (8.1 sq mi) area, Nauru is the third-smallest state on the list of countries and dependencies by area behind Vatican City and Monaco, making it the smallest state in the South Pacific Ocean, the smallest island state, and the smallest republic.  Its population is 11,347, making it the third smallest on the list of countries and dependencies by population, after the Vatican and Tuvalu.
Settled by people from Micronesia and Polynesia c.  1000 BC, Nauru was annexed and claimed as a colony by the German Empire in the late 19th century. After World War I, Nauru became a League of Nations mandate administered by Australia, New Zealand and the United Kingdom. During World War II, Nauru was occupied by Japanese troops, who were bypassed by the Allied advance across the Pacific. After the war ended, the country entered into United Nations trusteeship. Nauru gained its independence in 1968, and became a member of the Pacific Community (SPC) in 1969.
Nauru is a phosphate-rock island with rich deposits near the surface, which allowed easy strip mining operations. It has some remaining phosphate resources which, as of 2011, are not economically viable for extraction. When the phosphate reserves were exhausted, and the island's environment had been seriously harmed by mining, the trust that had been established to manage the island's wealth diminished in value. To earn income, Nauru briefly became a tax haven and illegal money laundering centre. From 2001 to 2008, and again from 2012, it accepted aid from the Australian Government in exchange for hosting the Nauru Regional Processing Centre, an offshore Australian immigration detention facility. As a result of heavy dependence on Australia, many sources have identified Nauru as a client state of Australia.
the Republic of Nauru