The InterCityExpress or ICE is a high-speed train, built by Siemens AG and others, operated mainly in Germany and neighboring countries, for example to Zürich, Switzerland or Vienna, Austria. ICE-trains also run to Liège and Brussels, Belgium and at lower speeds to Amsterdam, Netherlands. The Spanish railway operator RENFE also employs trains based on ICE 3 trains (Siemens Velaro). Wider versions were ordered by China for the Beijing-Tianjin high-speed rail (CRH 3) and by Russia for the Moscow - Saint Petersburg and the Moscow - Nizhny Novgorod routes (Velaro RUS).
Unlike the French TGV network, which radiates from Paris, the ICE network has multiple hubs. The ICE network is not a replacement of the InterCity network - it is an upgrade. ICE and IC trains usually share the same tracks. The main difference is the higher speed: while the ICE trains travel at the maximum line speed, IC trains are limited to 200 km/h. The only line that is not shared with other traffic is the 300 km/h Cologne-Frankfurt line due to its steep grades. In fact, it is limited to ICE3 train-sets, even the older ICE types need to take the longer route through the Rhine valley. The second 300 km/h line between Nuremberg and Ingolstadt, opened on 28 May 2006, does not have these restrictions. The line will also feature Germany's fastest commuter line at 200 km/h from December 2006 on.

Since the early 1970s, hundreds of kilometres of existing tracks have been upgraded to 200 km/h. As a result, ICE trains are able to use most conventional lines without losing too much time in the process. This allowed a rapid growth of the ICE network without the need to build several thousand kilometres of new high-speed lines. Even some high-speed lines (e.g. Cologne-Aachen at 250 km/h and Hamburg-Berlin at 230 km/h) are in fact upgraded conventional lines.