Line S9 is a north–south suburban metro line in the Nanjing Metro (Chinese: 南京地铁S9号线; pinyin: Nánjīng Dìtiě S-Jiǔ Hào Xiàn) system, which opened on December 30, 2017.

[4] It connects to Line S1 at Xiangyulunan and crosses Shijiu Lake on a 12 km (7.5 mi) long bridge between Mingjue and Tuanjiewei.

In June 2019 a few express trains started operating during rush hour, running non-stop between Xiangyulunan and Gaochun.

[6] Line S9 uses car Class B aluminum alloy trains with a maximum service speed of 120 km/h (75 mph).

[8] Unlike most Class B metro trains, each car only has 3 doors per side instead of 4, owing to the line's length and speed.