since 1964

The flag of Tanzania was adopted in 1964. It derives from the flags of Tanganyika and Zanzibar. The flag is divided diagonally by a yellow-edged black band from the lower hoist-side corner. The upper triangle (hoist side) is green and the lower triangle is blue.

The Green colour in the flag represents the natural vegetation present in the country.
The Golden colour represents rich mineral deposits of the country.
The Black colour represents the native swahili people of the country.
The Blue colour represents the numerous lakes and rivers and the Indian ocean.

source: wikipedia