Quebec Southern Railway
|Dates of operation||1900-1903–
|Predecessor||East Richelieu Valley Railway 1890-1900; Quebec, Montreal & Southern Railway 1906-1996|
|Successor||Quebec, Montreal & Southern Railway 1906-1996; Montreal, Maine & Atlantic Railway 2003-2014|
|Track gauge||4 ft 8 1⁄2 in (1,435 mm) standard gauge|
Quebec Southern Railway (reporting remark QSR) was two former railways operated in Quebec from 1900 to 1903 and again from 1996 to 2003. The railway was owned by American railway operators, but most of its existence was under Canadian ownership.
QSR began as East Richelieu Valley Railway in 1890 and 1895 it was acquired by United Counties Railways and in 1900 renamed as QSR when it was acquired by Rutland Railroad. The QSR name was short-lived as it was acquired by Delaware & Hudson Railway and renamed Quebec, Montreal & Southern Railway in 1906.
QMSR became part of Canadian National Railway's Quebec operations from 1929 to 1991 and then under rival Canadian Pacific Railway (CP) from 1991 to 1996, spun off by CP to Iron Road Railways which resurrected the QSR named in 1996.
The 2002 bankruptcy of Iron Road Railways saw QSR's assets sold in 2003. The rail line and property was acquired by the Montreal, Maine and Atlantic Railway (reporting mark MMA) and the QSR name disappeared once more.