Mainline
- Adana – Mersin Main Line
- Ahmedabad–Mumbai main line
- Arashiyama Main Line
- BCN Main Line
- Baden main line
- BitTorrent (software)
- Black Ivory
- Brighton Main Line
- Caledonian main line
- Canterbury Interior Main Line
- Cape Main Line
- Central line (disambiguation)
- Chatham Main Line
- Chennai Central–Mysuru main line
- Chiang Mai Main Line
- Chichibu Main Line
- Chikuhō Main Line
- Chiltern Main Line
- Chūō Main Line
- Cornish Main Line
- Dhaka Metro Rail
- East Coast Main Line
- Eiden Eizan Main Line
- Finnish Main Line
- Ford Mainline
- Fork (software development)
- Fukushima Rinkai Railway Main Line
- Gandhidham–Ahmedabad main line
- Glossary of chess
- Great Central Main Line
- Great Eastern Main Line
- Great Western Main Line
- Hakodate Main Line
- Hankyu Kyoto Main Line
- Hankyu Takarazuka Main Line
- Hankyū Kōbe Main Line
- Hanshin Main Line
- Hidaka Main Line
- Highland Main Line
- Hiroden Main Line
- Hokuriku Main Line
- Hotter than Hell (album)
- Howrah–Bardhaman main line
- Howrah–Chennai main line
- Howrah–Delhi main line
- Hōhi Main Line
- IRT Manhattan Main Line
- Kagoshima Main Line
- Kansai Main Line
- Karachi–Peshawar Line
- Keihan Main Line
- Keikyū Main Line
- Keisei Main Line
- Kisei Main Line
- Kyūdai Main Line
- MRT Line 2 (Dhaka Metro Rail)
- Main Line (Atlantic Coast Line Railroad)
- Main Line (Columbus to Chicago)
- Main Line (Columbus to Indianapolis via Bradford)
- Main Line (Long Island Rail Road)
- Main Line (NJ Transit)
- Main Line (New York to Hoffmans)
- Main Line (Pennsylvania Railroad)
- Main Line (Pittsburgh to St. Louis)
- Main Line (Reading Company)
- Main Line (Seaboard Air Line Railroad)
- Main Line (Sri Lanka)
- Main Line Broadcasting
- Main Line Health
- Main Line Preservation Group
- Main Line Subdivision
- Main Line for Europe
- Main Line of Mid-America
- Main Line of Public Works
- Main Line railway, Queensland
- Main Street Line (MATA Trolley)
- Main line (political)
- Main line (railway)
- Main line railway preservation
- Mainline (aeronautics)
- Mainline Corporation
- Mainline Drive-In
- Mainline Freight
- Mainline Linux
- Mainline Protestant
- Mainline Railways
- Mainliner (disambiguation)
- McKenna Mendelson Mainline
- Meitetsu Nagoya Main Line
- Metropolitan main line
- Midland Main Line
- Midland Mainline (train operating company)
- Mizushima Main Line
- Muroran Main Line
- Nagasaki Main Line
- Nankai Main Line
- Nayoro Main Line
- Nemuro Main Line
- New Delhi–Chennai main line
- Nippō Main Line
- North British Railway Main Line
- North Side main line
- Northern Main Line
- Ohmi Railway Main Line
- Old Main Line (disambiguation)
- Old Main Line Subdivision
- One Day (Australian band)
- Osaka Monorail Main Line
- PNR North Main Line
- PNR South Main Line
- Park Avenue main line
- Penrhyn Main Line class
- Philadelphia Main Line
- Philadelphia to Harrisburg Main Line
- Philadelphia-to-Washington Main Line
- Rumoi Main Line
- SEPTA Main Line
- San'in Main Line
- San'yō Main Line
- Sanyo Electric Railway Main Line
- Sekihoku Main Line
- Senmō Main Line
- Shin'etsu Main Line
- South Eastern Main Line
- South Humberside Main Line
- South Line, Tasmania
- South Side Main Line (Chicago Transit Authority)
- South Wales Main Line
- South West Main Line
- South Yorkshire Transport
- Southern Main Line
- Sōbu Main Line
- Sōtetsu Main Line
- Sōya Main Line
- Takayama Main Line
- Tasmanian Main Line Company
- Toyama Chihō Railway Main Line
- Toyohashi Railroad Azumada Main Line
- Trans-Korean Main Line
- Trunk (software)
- Trunkline (disambiguation)
- Tōhoku Main Line
- Tōkaidō Main Line
- Ubon Ratchathani Main Line
- Uetsu Main Line
- Washington to Atlanta Main Line
- Wessex Main Line
- West Anglia Main Line
- West Coast Main Line
- Western Main Line
- Ōigawa Railway Ōigawa Main Line
- Ōu Main Line