The Republic of the Congo, also known as Congo-Brazzaville, the Congo Republic or simply the Congo (its name from 1971 to 1997; the last ambiguously also referring to the neighbouring Democratic Republic of the Congo), is a country located on the western coast of Central Africa to the west of the Congo River. It is bordered to the west by Gabon, to the northwest by Cameroon, to the northeast by the Central African Republic, to the southeast by the Democratic Republic of the Congo, to the south by the Angolan exclave of Cabinda, and to the southwest by the Atlantic Ocean.

The region was dominated by Bantu-speaking tribes at least 3,000 years ago, who built trade links leading into the Congo River basin. From the 13th century, the present-day territory was dominated by a confederation led by Vungu which included Kakongo and Ngoyo. Loango emerged in the 16th century. In the late 19th century France colonised the region and incorporated it into French Equatorial Africa. The Republic of the Congo was established on 28 November 1958 and gained independence from France in 1960. It was a Marxist–Leninist state from 1969 to 1992, under the name People's Republic of the Congo (PRC). The country has had multi-party elections since 1992, but a democratically elected government was ousted in the 1997 Republic of the Congo Civil War. President Denis Sassou Nguesso, who first came to power in 1979, ruled until 1992 and then again since after his reinstatement.

The Republic of the Congo is a member of the African Union, the United Nations, La Francophonie, the Economic Community of Central African States, and the Non-Aligned Movement. It is the fourth-largest oil producer in the Gulf of Guinea, providing the country a degree of prosperity, with political and economic instability in some areas and unequal distribution of oil revenue nationwide. Its economy is dependent on the oil sector and economic growth has slowed since the post-2015 drop in oil prices.

Christianity is the most widely professed faith in the country. According to the 2024 rendition of the World Happiness Report, the Republic of the Congo is ranked 89th among 140 nations.

It is named after the Congo River whose name is derived from Kongo, a Bantu kingdom that occupied its mouth around the time the Portuguese first arrived in 1483 or 1484. The kingdom's name derived from its people, the Bakongo, an endonym said to mean "hunters" (Kongo: mukongo, nkongo).

During the period when France colonised it, it was known as the French Congo or Middle Congo. The Republic of the Congo, or simply the Congo, is a distinct country from the Democratic Republic of the Congo, also known as the DR Congo. Brazzaville's name derives from the colony's founder, Pierre Savorgnan de Brazzà, an Italian nobleman whose title referred to the town of Brazzacco, in the Italian comune of Moruzzo in Friuli Venezia Giulia, whose name derived from the Latin Brattius or Braccius, both meaning literally "arm".

Bantu-speaking peoples, who founded tribes during the Bantu expansions, mostly displaced and absorbed the earlier inhabitants of the region, the Pygmy people, about 1500 BC. The Bakongo, a Bantu ethnic group that occupied parts of what later became Angola, Gabon, and the Democratic Republic of the Congo, formed the basis for ethnic affinities and rivalries among those countries.^{[citation needed]}

By the 13th century, there were three main confederations of states in the western Congo Basin. In the east were the Seven Kingdoms of Kongo dia Nlaza, considered to be the oldest and most powerful, which likely included Nsundi, Mbata, Mpangu, and possibly Kundi and Okanga. South of these was Mpemba which stretched from modern-day Angola to the Congo River. It included various kingdoms such as Mpemba Kasi and Vunda. To its west across the Congo River was a confederation of three small states; Vungu (its leader), Kakongo, and Ngoyo. Some Bantu kingdoms—including those of the Kongo, the Loango, and the Teke—built trade links leading into the Congo Basin.