The P'yŏngnam Line is an electrified standard-gauge trunk line of the Korean State Railway in North Korea, linking P'yŏngyang with the port city of Namp'o and the hot springs at P'yŏngnam Onch'ŏn. The length of the line is 89.9 km (55.9 mi).

The P'yŏngnam Line serves as a connection between the various trunk lines starting at P'yŏngyang that serve the north and east of the country with the lines in the southwestern part of North Korea by means of a connection to the Sŏhae Kammun Line (West Sea Barrage Line). It connects to the Ryonggang Line and the Taean Line, as well as to the P'yŏngyanghwajŏn Line, the Chamjilli Line, the Posan Line, the Tojiri Line, the Namp'o Port Line, and, formerly, the Namdong Line.

The P'yŏngnam Line was originally built as two separate lines by two separate railway companies - the P'yŏngnam Line built by the Chosen Government Railway (Sentetsu), and the Onch'ŏn Line built by the privately owned Chosen P'yŏngan Railway.

In September 1909, Sentetsu began construction of a rail line running between P'yŏngyang and Chinnamp'o (nowadays Namp'o). Called the P'yŏngnam Line, it was opened for operations on 16 October 1910.

In the following years, a number of stations were opened along the line to expand the service: Kangsŏn Station on 1 July 1923; Kalch'ŏn Station on 1 May 1924; Taesŏng Station, 35.2 km (21.9 mi) from P'yŏngyang between Kangsŏ and Ryonggang, was opened on 1 November 1925 and subsequently closed; Choch'on station was opened on 11 February 1934, but a year later was dismantled and moved 1.2 km (0.75 mi) south, becoming today's Ch'ilgol Station; Taep'o Station, 13.3 km (8.3 mi) from P'yŏngyang Station between Choch'on and Taep'yŏng Stations in Man'gyŏngdae-guyŏk, P'yŏngyang, was opened on 10 January 1944 and subsequently closed; and Pot'onggang Station on 21 March 1944.

On 8 July 1938, the Chosen P'yŏngan Railway opened the 34.7 km (21.6 mi) Onch'ŏn Line from Chinnamp'o, terminus of Sentetsu's P'yŏngnam Line, to Ryonggang Onch'ŏn, running two daily passenger trains to connect the hot springs there with Pot'onggang Station in P'yŏngyang and with Tŏkch'ŏn on the West Chosen Central Railway's Seoseon Line.

After the partition of Korea, the two lines were within the Soviet zone of occupation, and both lines - together with all others within the Soviet zone - were nationalised by the Provisional People’s Committee for North Korea on 10 August 1946, and operated by the Korean State Railway following the establishment of the DPRK, which merged the Onch'ŏn Line into the P'yŏngnam Line. The line was heavily damaged during the Korean War, but was subsequently rebuilt and expanded, with the construction of Sinnamp'o Station to serve glass factories and shipbuilders located there.

The mainline between P'yŏngyang and Namp'o was electrified in December 1979.