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 and microstate in Oceania, in the Central Pacific. Its nearest neighbour is Banaba Island in Kiribati, 300 km (190 mi) to the east. It further lies northwest of Tuvalu, 1,300 km (810 mi) northeast of 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 km2 (8.1 sq mi) area, Nauru is the third-smallest country in the world behind Vatican City and Monaco, making it the smallest republic as well as the smallest island nation. Its population of about 10,000 is the world's second-smallest (not including colonies or overseas territories), after Vatican City.

Settled by people from Micronesia circa 1000 BCE, 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, and was 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 (PC) in 1969.

Nauru is a phosphate-rock island with rich deposits near the surface, which allowed easy strip mining operations for over a century, though at the cost of seriously harming the island's environment. The phosphate was exhausted in the 1990s, and the remaining reserves are not economically viable for extraction. A trust established to manage the island's accumulated mining wealth, set up for the day the reserves would be exhausted, has 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, a controversial offshore Australian immigration detention facility. As a result of heavy dependence on Australia, some sources have identified Nauru as a client state of Australia. The sovereign state is a member of the United Nations, Commonwealth of Nations and the African, Caribbean, and Pacific Group of States.

Kiribati (), officially the Republic of Kiribati (Gilbertese: [Ribaberiki] Kiribati), is an independent island nation in the central Pacific Ocean. The permanent population is over 119,000 (2020), more than half of whom live on Tarawa atoll. The state comprises 32 atolls and one raised coral island, Banaba. There is a total land area of 811 square kilometres (313 square miles) dispersed over 3.5 million km2 (1.4 million sq mi) of ocean.

Their spread straddles the equator and the 180th meridian, although the International Date Line goes around Kiribati and swings far to the east, almost reaching the 150° W meridian. This brings Kiribati's easternmost islands, the southern Line Islands south of Hawaii, into the same day as the Gilbert Islands and places them in the most advanced time zone on Earth: UTC+14. Kiribati is the only country in the world to be situated in all four cardinal hemispheres.Kiribati gained its independence from the United Kingdom, becoming a sovereign state in 1979. The capital, South Tarawa, now the most populated area, consists of a number of islets, connected by a series of causeways. These comprise about half the area of Tarawa atoll. Prior to its independence, the country had exported phosphate; however, those mines are no longer viable with fisheries and export of copra driving much of the economy. Kiribati is one of the least developed countries in the world and is highly dependent on international aid for its economy.

Kiribati is a member of the Pacific Community (SPC), Commonwealth of Nations, the IMF, the World Bank, the OACPS and became a full member of the United Nations in 1999 and also a member of the Pacific Islands Forum. As an island nation, the islands are very vulnerable to climate change and addressing climate change has been a central part of its international policy, as a member of the Alliance of Small Island States.