Ceratium furca is a species of marine dinoflagellates. This species has a straight body which is 70-200 µm long and 30-50 µm wide, with the epitheca gradually tapering into an anterior horn. C. furca has long spines, and is an 'armoured' species with a theca of thick cellulose plates. The cells are nearly flat, with the ventral side concave and the dorsal side being convex. C. furca is found worldwide.