An undersea connection system for connecting together at least three high voltage or very high voltage undersea electric cables comprises an outer cage defining a connection space; and a connection fitting comprising a conductive connection electrode that presents a junction node from which there extend at least three branches. Each of the at least three branches of the conductive electrode includes a male terminal portion that is connected to a respective one of the electric cables in a connection zone about which there is mounted a connection sleeve made of pre-molded insulating material that receives, via its ends, firstly the male terminal portion of one of the branches of the conductive electrode, and secondly the connection end of one of the electric cables.