Line S2 (Chinese: 南京地铁S2号线; pinyin: Nánjīng Dìtiě S-Èr Hào Xiàn) is a suburban rapid transit line in the Nanjing Metro system which is currently under construction. The initial phase is expected to open in 2027.^[1] The line will have passing loops for express and local services with express trains completing travel across the whole line in 30 minutes.^[2]

In 2020, the mayors of Nanjing and Ma'anshan Cities jointly signed the "Ningma Intercity Railway Co-construction Cooperation Agreement".^[3]

The tender notice for the survey, design and review of the Nanjing-Ma'anshan intercity railway was released in September 2021. The first phase of the Nanjing section will have 8 stations and 26.9 kilometers, and the second phase will have 4 stations and 11.2 kilometers.^[4]

Construction of the Ma'anshan section, an elevated line from Cihu to Dangtu South, started on 30 December 2020.^[5] The Nanjing section started construction on December 28, 2021.^[6]