The ALCO RSD-5 is a diesel-electric locomotive rated at , that rode on a pair of three-axle trucks, having a C-C wheel arrangement.
Basically an upgraded version of the earlier ALCO RSD-4, and used in much the same manner as its four-axle counterpart, the ALCO RS-3, the six-motor design allowed better tractive effort at lower speeds.
As of 2024, there are only two unrebuilt RSD-5s known to be in existence.
Two former RSD-5s (rebuilt as RSD-12's) built for the Southern Pacific survive at the Southern California Railway Museum (SP #2954 and SP #2958).