Mossendjo is a town in the Niari Valley of the Republic of the Congo. It lies within the Chaillu Massif. Its principle activities are hunting and agriculture. The main products cultivated are manioc, coffee, cocoa, peanuts, banana, tobacco and rice. The Congo-Ocean Railway (COR; French: Chemin de fer Congo-Océan, CFCO), built in the 1920s, passes through Mossendjo.

Unemployment rates are high in the region, due to the lack of industrial job opportunities.

Mossendjo is a 5-hour drive north (175 km) from Dolisie on dirt roads. However, there is an old airstrip that can be used if you are chartering a plane.

The main road in the town is paved. However, all surrounding are dirt roads.

The market in Mossendjo has a wide selection of fruit and vegetables. Make sure to go early because after noon, the shops start to close up.