Kogin Dja (wanda kuma aka fi sani da Kogin Ngoko) rafi ne a yammacin Afirka ta yamma. Tana daga cikin iyakar Kamaru – Jamhuriyar Kongo kuma tana da kwatankwacin kilomita 720 (mil 450). Tashi daga kudu maso gabashin garin Abong-Mbang da ke kudu maso gabashin Kamaru, Ajiyar Fajal na Dja, wanda aka sanya wa suna UNESCO a Duniya a cikin 1987, ya kasance a gefen bankunan babban hanyar. Tana kare ɗayan mafi girman yankuna na dazuzzuka masu zafi a Afirka. Kafa iyakarta ta halitta, kuma kusan kusan kewayen wurin ajiyar (banda kudu maso yamma), tsaunuka suna tafiya ta hanyar kogin a yankin kudu na ajiyar na kilomita 60 kuma suna da alaƙa da wani ɓangare na kogin da ya karye ta hanzari da ruwa. Bayan bin tafarkinsa a cikin wurin, Dja yana gudana kusan kudu maso gabas bayan Moloundou, ƙasa da ƙananan jiragen ruwa zasu iya tafiya. A Ouesso, a Jamhuriyar Congo, ya ɓuɓɓugo zuwa Kogin Sangha. Kowace shekara, mafarauta suna zuwa Dja zuwa tsakiyar Nki National Park, inda hauren giwayen ya yi yawa.