超音波马达为一种利用机械振动与摩擦力来产生推力的致动器，当振动频率超过20kHz（人体感应的界限）时，此种致动器即称为超音波马达。

在认识超音波马达前，首先必须了解压电效应，因为超音波马达所需要的振动源即由具有压电性的材料所提供。

压电效应（piezoelectric effect）是一种机械能与电能之间的互相转移现象。1880年时，法国的皮埃尔·居里(Pierre Curie)和雅克·居里(Jacques Curie)兄弟在研究焦电现象(pyroelectric effect)与晶体对称性关系的研究时，发现对某类晶体(非对称晶格结构)施加机械压力，可以在其表面上得到电荷，且电位量与其所施加的应力呈现正比关系，即正压电效应（Direct Piezoelectric Effect)。

An ultrasonic motor is a type of electric motor powered by the ultrasonic vibration of a component, the stator, placed against another component, the rotor or slider depending on the scheme of operation (rotation or linear translation). Ultrasonic motors differ from piezoelectric actuators in several ways, though both typically use some form of piezoelectric material, most often lead zirconate titanate and occasionally lithium niobate or other single-crystal materials. The most obvious difference is the use of resonance to amplify the vibration of the stator in contact with the rotor in ultrasonic motors. Ultrasonic motors also offer arbitrarily large rotation or sliding distances, while piezoelectric actuators are limited by the static strain that may be induced in the piezoelectric element.