A millwright is a craftsperson or skilled tradesperson who installs, dismantles, maintains, repairs, reassembles, and moves machinery in factories, power plants, and construction sites.

The term millwright (also known as industrial mechanic) is mainly used in the United States, Canada and South Africa to describe members belonging to a particular trade. Other countries use different terms to describe tradesmen engaging in similar activities. Related but distinct crafts include machinists, mechanics and mechanical fitters.

As the name suggests, the original function of a millwright was the construction of flour mills, sawmills, paper mills and fulling mills powered by water or wind, made mostly of wood with a limited number of metal parts. Since the use of these structures originates in antiquity, millwrighting could arguably be considered one of the oldest engineering trades and the forerunner of modern mechanical engineering.

In modern usage, a millwright is engaged with the erection of machinery. This includes such tasks as leveling, aligning, & installing machinery on foundations or base plates, or setting, leveling, & aligning electric motors or other power sources such as turbines with the equipment, which millwrights typically connect with some type of coupling.