Mainline, Main line, or Main Line may refer to:
Transportation
Railway
Main line (railway), the principal artery of a railway system
Main line railway preservation, the practice of operating preserved trains on an operational railway network
Asia
Bangladesh
Main line, MRT Line 2 of Dhaka Metro Rail
India
Ahmedabad–Mumbai main line
Chennai Central–Mysuru main line
Gandhidham–Ahmedabad main line
Howrah–Bardhaman main line
Howrah–Chennai main line, between Chennai and Kolkata
Howrah–Delhi main line
New Delhi–Chennai main line
Japan
Korea
Trans-Korean Main Line
Pakistan
Karachi–Peshawar Line, also referred to as Main Line 1
Philippines
PNR North Main Line
PNR South Main Line
Sri Lanka
Main Line (Sri Lanka)
Thailand
Chiang Mai Main Line, between Bangkok and Chiang Mai
Ubon Ratchathani Main Line, between Ban Phachi Junction and Ubon Ratchathani
Turkey
Adana – Mersin Main Line
Europe
Main Line for Europe
Finland
Finnish Main Line, between Helsinki and Oulu
Germany
Baden main line, between Baden and Constance
Sweden
Northern Main Line, between Gävle or Storvik and Ånge
Southern Main Line, between Malmö and Katrineholm
Western Main Line, between Stockholm and Gothenburg
United Kingdom
Brighton Main Line
Caledonian main line
Chatham Main Line
Chiltern Main Line
Cornish Main Line
East Coast Main Line
Great Central Main Line
Great Eastern Main Line
Great Western Main Line
Highland Main Line
Main Line Preservation Group, an organisation that eventually became the Great Central Railway heritage railway
Mainline Freight, a defunct UK railfreight company
Midland Main Line
Midland Mainline (train operating company), a defunct UK train-operating company
North British Railway Main Line
Penrhyn Main Line class, three narrow-gauge steam locomotives built for the Penrhyn Quarry Railway
South Eastern Main Line
South Humberside Main Line, between Doncaster and Cleethorpes