The Siemens Desiro is a family of diesel or electric multiple unit passenger trains developed by Siemens Mobility, a division of the German Siemens AG conglomerate. The main variants are the Desiro Classic, Desiro ML, Desiro UK and the later Desiro City, Desiro HC and Desiro RUS. The trains are mostly used for commuter and regional services, and their rapid acceleration makes them suitable for services with short distances between stations. The design is flexible, and has become common in many European countries.

A diesel multiple unit or DMU is a multiple-unit train powered by on-board diesel engines. A DMU requires no separate locomotive, as the engines are incorporated into one or more of the carriages. Diesel-powered single-unit railcars are also generally classed as DMUs. Diesel-powered units may be further classified by their transmission type: diesel–mechanical DMMU, diesel–hydraulic DHMU, or diesel–electric DEMU.