The is a railway line in Nagano Prefecture, Japan, operated by the East Japan Railway Company (JR East). It connects Shinonoi Station in Nagano with Shiojiri Station in Shiojiri.
The line is a corridor between the Shinetsu Main Line and the Chà «à  Main Line. All the limited express trains on the Shinonoi Line come from the Chà «à  Main Line: Azusa from Tokyo and Shinano from Nagoya.
All stations are located in Nagano Prefecture.
A passing loop is located in Azumino, known as . It has two tracks.
A switchback is located in Azumino, known as
A switchback is located in Azumino, known as
The Shinonoi to Nishijo section opened in 1900, and was extended via Matsumoto to Shiojiri in 1902.
The Shiojiri to Matsumoto section was double-tracked between 1961 and 1965, with the Tazawa to Akashina section double-tracked in 1966. The Akashina to Nishijo section was also double-tracked, but the original line was decommissioned in 1988.
The Shiojiri to Matsumoto section was electrified in 1964/5, and extended to Shinonoi in 1973, CTC signalling being commissioned on the entire line the previous year.
Station numbering was introduced on the Nagano area from February 2025, with Shinonoi Line stations numbered using the prefix "SN". Numbers increase towards Shinonoi.