机务段，是中国铁路负责机车运用、维护的一线运输单位。2005年3月18日之前，机务段隶属于各铁路分局，一般为副处级单位；此后，机务段直属于铁路局，为处级单位。

在册职工平均10人对应编制运用1台机车。

Motive power depot, usually abbreviated to MPD, or railway depot is a term given to places where usually locomotives are housed when not being used, and also repaired and maintained. They were originally known as "running sheds", "engine sheds", or, for short, just sheds. Facilities are provided for refuelling and replenishing water, lubricating oil and grease and, for steam engines, disposal of the ash. There are often workshops for day to day repairs and maintenance, although locomotive building and major overhauls are usually carried out in the locomotive works.