Gnanmangui (also spelled Gnamandji) is a bakwé city in south-western Ivory Coast. It is a sub-prefecture of Méagui Department in Nawa Region, Bas-Sassandra District.
The western third of the sub-prefecture is located in Taï National Park.
Gnanmangui was a commune until March 2012, when it became one of 1,126 communes nationwide that were abolished.
In 2014, the population of the sub-prefecture of Gnanmangui was 116,476.
The twenty five villages of the sub-prefecture of Gnanmangui and their population in 2014 are: