Liège to 's-Hertogenbosch train with Regional-Express

Regional-Express (RE, or REX in Austria) is a type of regional train service found in Germany, Luxembourg, and Austria. It functions as a semi-fast train, making fewer stops than a Regionalbahn or S-Bahn but more than an Intercity or Intercity Express. RE services typically reach top speeds of 160 km/h, with some reaching 200 km/h on high-speed lines. While initially operated by DB Regio, many lines are now run by various private operators. These trains often use double-deck cars with electric or diesel locomotives.

The term "Regional" can refer to different train companies and services depending on the country. In Germany, "Regionalbahn" (RB) is a type of local passenger train that typically stops at all stations on a given line, connecting cities to their surrounding areas. Many RB trains are operated by DB Regio, a division of Deutsche Bahn, but other companies also run these services.