听诊器是一种医学仪器，用以聆听身体内的声音，例如：心脏、呼吸及肠胃等等。听诊器由法国医生雷奈克（Laennec）于1816年创造，于1819年公布。

听诊器是医生检查病人、诊断疾病的一种重要方法。听诊器主要由铜、橡胶管、弹簧片和听头等材料组成。听诊器更分“单用听诊器”、“双用听诊器”、“三用听诊器”、“立式听诊器”和“多用听诊器”等多种，用于在不同环境听诊不同状况的病人。听头也分多种，例如“扁形听诊头”用于听诊高音调的杂音；“大小双功能扁形听头”用于探测低频心音、小儿心音等；“钟形瞬诊头”可听到腹中胎儿心跳；“表式听诊器”用于听诊手腕的脉搏声响。

The stethoscope is an acoustic medical device for auscultation, or listening to the internal sounds of an animal or human body. It typically has a small disc-shaped resonator that is placed against the chest, and two tubes connected to earpieces. It is often used to listen to lung and heart sounds. It is also used to listen to intestines and blood flow in arteries and veins. In combination with a sphygmomanometer, it is commonly used for measurements of blood pressure. Less commonly, "mechanic's stethoscopes" are used to listen to internal sounds made by machines, such as diagnosing a malfunctioning automobile engine by listening to the sounds of its internal parts. Stethoscopes can also be used to check scientific vacuum chambers for leaks, and for various other small-scale acoustic monitoring tasks. A stethoscope that intensifies auscultatory sounds is called phonendoscope.