Lastoursville or Mandji is a city in east-central Gabon, lying on the Ogooué River, the Trans-Gabon Railway and the N3 road.

It was founded as a slave depot named Mandji, renamed Maadiville in 1883 before being named for François Rigail de Lastours in 1886.

The town lies at an elevation of 206 m. Occupying a 90-sq-km site, there are more than 40 caves identified,[1] located in dense primary rainforest close to town.

Traces of human activity dates back 7000 years, when the caves were used in rituals.

[2] The caves were added to the UNESCO World Heritage Tentative List on October 20, 2005 in the Mixed (Cultural + Natural) category.