Line 4 of the Hanoi Metro (Thang Long Line) is a planned metro line that will form a loop around the city and interchange with every line.

Line name: Thang Long Line.
Total length: 54 km.
Number of stations: 41 stations.

Line 4 passes through Me Linh, Dong Anh, Hoang Mai, Ring road 2.5, Co Nhue, and Lien Ha. The line is not a complete circle, but the circle is closed by Line 7.