The Main Railway (German: Mainbahn, pronounced 'mine barn') is a 37.5 km-long double-track electrified railway line, which runs on the south side of the river Main from Mainz to Frankfurt central station.

It thereby put itself into competition with the parallel Taunus Railway, which runs on the right bank of the Main.

The concession for building and operating the line was awarded by Grand Duchy of Hesse on 15 August 1861 and by the senate of the Free City of Frankfurt on 17 January 1862.

Since 1999 the Raunheim Mönchwald–Raunheim Mönchhof connecting curve has provided a connection with the Cologne–Frankfurt high-speed rail line, allowing long-distance trains to and from on the Left Rhine line to use the Frankfurt Airport long-distance station.

Regional and Rhine-Main S-Bahn services run between Kelsterbach station and Frankfurt-Schwanheim Fernbahn junction over the Airport loop.