The ALCO RS-11 is a class of diesel-electric locomotive rated at 1,800 hp (1.34 MW), that rode on two-axle trucks, having a B-B wheel arrangement.

Featuring a V-12, 1,800 hp (1,300 kW) 251B diesel engine, the RS-11 was ALCO's answer to EMD's very successful GP9.

The turbocharged RS-11 accelerated faster, had a higher tractive effort rating and typically used less fuel than the competition.

Montreal Locomotive Works also built 351 nearly identical units, known as the RS-18, for the Canadian market.

[2] While the RS-11 benefited from the increased power and reliability offered with ALCO's new 251B engine, and was arguably a more advanced product than the GP9, its market acceptance was disappointing against the reputation EMD's locomotives had made for superior reliability.