RB 23 is the designation of several regional rail services in Germany:
, operated by DB Regio Mitte between Mayen Ost and Limburg (Lahn) , operated by DB Regio Nordost between BER Airport – Terminal 1-2 and Golm , operated by DB Regio Nordost between Züssow and Świnoujście Centrum , operated by DB Regio NRW between Bad Münstereifel and Euskirchen , operated by Oberpfalzbahn between Regensburg and Marktredwitz or Neustadt (Waldnaab)