The Nagareyama Line (流山線, Nagareyama-sen) is a commuter rail line in Chiba Prefecture, Japan, operated by Ryutetsu (流鉄株式会社, Ryūtetsu kabushiki-kaisha) between Mabashi Station in Matsudo and Nagareyama Station in Nagareyama. The line and the operator company was called the Sōbu Nagareyama Line (総武流山線, Sōbu Nagareyama-sen) and Sōbu Nagareyama Electric Railway (総武流山電鉄, Sōbu Nagareyama Dentetsu) respectively until the renaming on August 1, 2008.^[1] The present line name was the most popular short name of the line. It was also called Ryūden (流電).

This is the only line Ryūtetsu operates, making the company unique for being an independent railway operator with just a single 5.7 km line and no major subsidiary businesses (unlike Yamaman or The Oriental Land Company and their Disney Resort Line). The short line functions as a link between the centre of the city of Nagareyama and the East Japan Railway Company (JR East) Jōban Line. However, after the opening of the Tsukuba Express on August 24, 2005, ridership fell sharply. Suica and PASMO contactless smart cards cannot be used, and Ryūtetsu reportedly has no plans to introduce the system on the line.

• Double-tracking: None
• Railway signalling: Automatic Train Stop
• Passing loop: Kogane-Jōshi Station

The company was incorporated on November 7, 1913 as Nagareyama Light Railway (流山軽便鉄道, Nagareyama Keiben Tetsudō) and opened a 762 mm (2 ft 6 in) gauge railway on March 14, 1916. The company renamed Nagareyama Railway (流山鉄道, Nagareyama Tetsudō) in November 1922 and rebuilt the railway track to 1,067 mm (3 ft 6 in) gauge in 1924.^[1]

The company name was again changed to Nagareyama Electric Railway (Nagareyama Denki Tetsudō) in 1949, to Nagareyama Electric Railway (Nagareyama Dentetsu) in 1967, to Sōbu Nagareyama Electric Railway in 1971 and to Ryūtetsu in 2008.^[1]

All stations are in Chiba Prefecture.