超音波（Ultrasound、超音波）是指任何声波或振动，其频率超过人类耳朵可以听到的最高阈值20kHz（千赫）。超音波由于其高频特性而被广泛应用于众多领域，比如金属探伤，工件清洗等。

某些动物，如狗只、海豚、以及蝙蝠等等都有着超乎人类的耳朵，也因此可以听到超声波。亦有人利用这个特性制成能产生超音波来呼唤狗只的犬笛。

所谓超音波，只透过具有弹性与惯性介质，如空气，当空气本身一旦产生膨胀或压缩时，透过其分子的运动而有波动的传拨产生。因此，音波无法在真空中进行传播。人类听觉能察觉波动，称之为声音。此时音波，即称之为可听波。

Ultrasounds are sound waves with frequencies higher than the upper audible limit of human hearing. Ultrasound is no different from 'normal' (audible) sound in its physical properties, except in that humans cannot hear it. This limit varies from person to person and is approximately 20 kilohertz (20,000 hertz) in healthy, young adults. Ultrasound devices operate with frequencies from 20 kHz up to several gigahertz.