Where in the world?
The flag of Gabon has three horizontal stripes of green, yellow, and blue.

Gabon

Population: 2,225,728

Region: Africa

Subregion: Middle Africa

Capital: Libreville

Top Level Domain: .ga

Currencies: Central African CFA franc

Border countries

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 the Congo has a green field with a yellow diagonal stripe from the lower hoist-side to the upper fly-side.

Congo

Population: 5,518,092

Region: Africa

Capital: Brazzaville
The flag of Equatorial Guinea has three horizontal stripes of green, white, and red with a blue triangle at the hoist side containing a white star.

Equatorial Guinea

Population: 1,402,985

Region: Africa

Capital: Malabo