Kogin Gambiya (wanda a da ake kira da Kogin Gambra) babban kogi ne a Afirka ta Yamma, yana tafiyar kilomita 1,120 (700 mi) daga tsaunin Fouta Djallon da ke arewacin Guinea ta yamma zuwa Senegal da Gambiya zuwa Tekun Atlantika a garin Banjul. Ana iya kewaya shi zuwa kusan rabin wannan tsayin. Kogin yana da alaƙa da Gambiya, ƙaramar ƙasa a cikin yankin Afirka, wanda ya ƙunshi ƙasa da rabin rabin kogin da bankunan biyu. Daga Fouta Djallon, kogin ya ratsa arewa maso yamma zuwa yankin Tambacounda na Senegal, inda ya ratsa ta cikin Parc National du Niokolo Koba, sannan Nieri Ko da Koulountou [fr] suka haɗu kafin shiga Gambiya a Fatoto. A wannan lokacin, kogin yana tafiyar da yamma gaba daya, amma a wata hanya mai ban mamaki tare da kwalliya da yawa, kuma kusan kilomita 100 daga bakinsa a hankali yana fadada, zuwa sama da kilomita 10 fadi inda ya hadu da teku. Ya zuwa shekarar 2020, akwai hanyar tsallaka tsintsiya madaidaiciya guda ɗaya, Gadar Senegambia kusa da garuruwan Farafenni da Soma a Gambiya.