Nigeria, officially the Federal Republic of Nigeria, is a federal constitutional republic comprising 36 states and its Federal Capital Territory, Abuja. The country is located in West Africa and shares land borders with the Republic of Benin in the west, Chad and Cameroon in the east, and Niger in the north. Its coast in the south lies on the Gulf of Guinea on the Atlantic Ocean.
The highest point in Nigeria is Chappal Waddi at 2,419 m. The main rivers are the Niger and the Benue River which converge and empty into the Niger Delta, one of the world's largest river deltas and the location of a large area of Central African Mangroves. Nigeria has a varied landscape. The far south is defined by its tropical rainforest climate, where annual rainfall is 60 to 80 inches a year. In the southeast stands the Obudu Plateau. Coastal plains are found in both the southwest and the southeast. This forest zone's most southerly portion is defined as salt water swamp, also known as a mangrove swamp because of the large amount of mangroves in the area. North of this is fresh water swamp, containing different vegetation from the salt water swamp, and north of that is rain forest.

Over 500 languages have been recorded as being spoken in Nigeria. In some areas of Nigeria, ethnic groups speak more than one language. The official language of Nigeria, English, was chosen to facilitate the cultural and linguistic unity of the country. The choice of English as the official language was partially related to the fact that a part of the Nigerian population spoke English as a result of British colonisation that ended in 1960.
Nigeria is home to a variety of religions which tend to be concentrated regionally. This situation accentuates regional and ethnic distinctions and has often been seen as a source of sectarian conflict amongst the population. Though Nigeria is divided about equally between followers of Islam and Christianity, across Nigeria there is widespread belief, albeit suppressed for political reasons, in traditional religious practices.

Population in Nigeria increased from 1990 to 2008 by 57 million a 60% growth rate. Nigeria is the most populous country in Africa and accounts for about 18% of the continent's total population, however, exactly how populous is a subject of speculation.