Line S4, commonly known as Nanjing–Chuzhou line or Chuzhou Rail Transit Line 1, is a rapid transit line of Nanjing Metro connecting Chuzhou and Nanjing in both Anhui and Jiangsu provinces of China. It is 46.2 kilometres (28.7 mi) long and has a maximum operating speed of 120 kilometres per hour (75 mph). Currently most of the Chuzhou section is opened on 28 June 2023, with a little rest sections in Chuzhou and Nanjing are still under construction.