South Line may refer to:
- Glasgow South Western Line, Scotland
- Main South Line, New Zealand
- Østfold Line, Norway
- PNR South Main Line, Philippines
- Sounder South Line, Washington, United States
- South Eastern Main Line, England
- South-Link Line, Taiwan
- South Line, Chennai Suburban, India
- Main Southern railway line, New South Wales, Australia
- South Line, a former passenger line in Sydney, Australia, now split into:
- South West Main Line, England
- South West Line, Chennai Suburban, India
- West South Line, Chennai Suburban, India
- South Line, Tasmania, Australia