Nigeria, officially the Federal Republic of Nigeria, is a country in West Africa. It is situated between the Sahel to the north and the Gulf of Guinea in the Atlantic Ocean to the south. It covers an area of 923,769 square kilometres (356,669 sq mi). With a population of more than 230 million, it is the most populous country in Africa, and the world's sixth-most populous country. Nigeria borders Niger in the north, Chad in the northeast, Cameroon in the east, and Benin in the west. Nigeria is a federal republic comprising 36 states and the Federal Capital Territory, where its capital, Abuja, is located. The largest city in Nigeria by population is Lagos, one of the largest metropolitan areas in the world and the largest in Africa.

Nigeria has been home to several indigenous material cultures, pre-colonial states and kingdoms since the second millennium BC. The Nok culture, c. 1500 BC, marks one of the earliest known civilizations in the region. The Hausa Kingdoms inhabited the north, with the Edo Kingdom of Benin in the south, Igbo Kingdom of Nri in the southeast and in the southwest, the Oyo Empire. The present day territory of Nigeria was home to a vast array of city-states. In the early 19th century the Fula jihads culminated in the Sokoto Caliphate. The modern state originated with British colonialization in the 19th century, taking its present territorial shape with the merging of the Southern Nigeria Protectorate and the Northern Nigeria Protectorate in 1914. The British set up administrative and legal structures and incorporated traditional monarchs as a form of indirect rule. Nigeria became a formally independent federation on 1 October 1960. It experienced a civil war from 1967 to 1970, followed by a succession of military dictatorships and democratically elected civilian governments until achieving a stable government in the 1999 Nigerian presidential election.

Nigeria is a multinational state inhabited by more than 250 ethnic groups speaking 500 distinct languages, all identifying with a wide variety of cultures. The three largest ethnic groups are the Hausa in the north, Yoruba in the west, and Igbo in the east, together constituting over 60% of the total population. The official language is English, chosen to facilitate linguistic unity at the national level. Nigeria's constitution ensures de jure freedom of religion, and it is home to some of the world's largest Muslim and Christian populations. Nigeria is divided roughly in half between Muslims, who live mostly in the north part of the country, and Christians, who live mostly in the south; indigenous religions, such as those native to the Igbo and Yoruba ethnicities, are in the minority.

Nigeria is a regional power in Africa and a middle power in international affairs. Nigeria's economy is the fourth-largest in Africa, the 53rd-largest in the world by nominal GDP, and 27th-largest by PPP. Nigeria is often referred to as the Giant of Africa by its citizens due to its large population and economy, and is considered to be an emerging market by the World Bank. Nigeria is a founding member of the African Union and a member of many international organizations, including the United Nations, the Commonwealth of Nations, NAM, the Economic Community of West African States, Organisation of Islamic Cooperation and OPEC. It is also a member of the informal MINT group of countries and is one of the Next Eleven economies.

The name Nigeria derives from the Niger River running through the country. This name was coined on 8 January 1897, by the British journalist Flora Shaw. The neighboring Republic of Niger takes its name from the same river. The origin of the name Niger, which originally applied to only the middle reaches of the Niger River, is uncertain. The word is likely an alteration of the Tuareg name egerew n-igerewen used by inhabitants along the middle reaches of the river around Timbuktu before 19th-century European colonialism. Before Flora Shaw suggested the name Nigeria, other proposed names included Royal Niger Company Territories, Central Sudan, Niger Empire, Niger Sudan, and Hausa Territories.

Kainji Dam excavations showed ironworking by the 2nd century BC. The transition from Neolithic times to the Iron Age was accomplished without intermediate bronze production. Some have suggested the technology moved west from the Nile Valley. But the Iron Age in the Niger River valley and the forest region appears to predate the introduction of metallurgy in the upper savanna by more than 800 years, as well as predating it in the Nile Valley. More recent research suggests that iron metallurgy was developed independently in Africa.

The Nok civilization thrived between 1,500 BC and AD 200. It produced life-sized terracotta figures that are some of the earliest known sculptures in Africa and smelted iron by about 550 BC and possibly a few centuries earlier. Evidence of iron smelting has also been excavated at sites in the Nsukka region of southeast Nigeria: dating to 2000 BC at the site of Lejja and to 750 BC at the site of Opi.

The Kano Chronicle highlights an ancient history dating to around 999 AD of the Hausa Sahelian city-state of Kano, with other major Hausa cities (or Hausa Bakwai) of Daura, Biram, Katsina, Kingdom of Zazzau, Rano, and Gobir all having recorded histories dating back to the 10th century. With the spread of Islam from the 7th century AD, the area became known as Sudan or as Bilad Al Sudan (English: Land of the Blacks). Since the populations were partially affiliated with the Arab Muslim culture of North Africa, they began trans-Saharan trade and were referred to by the Arabic speakers as Al-Sudan (meaning "The Blacks") as they were considered an extended part of the Muslim world. There are early historical references by medieval Arab and Muslim historians and geographers which refer to the Kanem–Bornu Empire as the region's major centre for Islamic civilization.^{[citation needed]}