Where in the world?
The flag of Nigeria has three vertical stripes of green, white, and green.

Nigeria

Population: 206,139,587

Region: Africa

Subregion: Western Africa

Capital: Abuja

Top Level Domain: .ng

Currencies: Nigerian naira

Border countries

The flag of Benin has two horizontal bands of yellow and red with a green vertical band on the hoist side.

Benin

Population: 12,123,198

Region: Africa

Capital: Porto-Novo
The flag of Cameroon has three vertical stripes of green, red, and yellow with a yellow star in the center.

Cameroon

Population: 26,545,864

Region: Africa

Capital: Yaoundé
The flag of Chad has three vertical stripes of blue, yellow, and red.

Chad

Population: 16,425,859

Region: Africa

Capital: N'Djamena
The flag of Niger has three horizontal stripes of orange, white, and green with an orange circle in the center.

Niger

Population: 24,206,636

Region: Africa

Capital: Niamey