The Deutsche Bahn Class 423 EMU is a light-weight articulated electric railcar for S-Bahn commuter networks in Germany. The train has similar dimensions to its predecessor, the Class 420 EMU, but is significantly lighter and has one large passenger compartment, while that of the 420 is divided into three parts. The 423 additionally has six doors in each carriage, which is down from eight on the 420. They are numbered from 423 001 to 423 462.

The Class 420 is a commuter electric multiple unit train type in service on German S-Bahn networks since 1972. Their use in Munich during the 1972 Summer Olympics earned them the colloquial name Olympiatriebwagen.