退磁（英语：Degaussing），又称为消磁，是一种减少或消除永久磁铁剩磁的方式，其英文名称可能是得名自磁的单位高斯。因为磁滞现象，多半无法将磁场完全降到零；因此退磁一般会引入一个很小的已知磁场，称为偏移量。退磁可用来减少CRT显示器的磁场，也用来清除磁保存组件中的数据。

退磁可以用许多方式进行，包括：

• 加热到居里温度以上。
• 将材料放在磁场强度大于矫顽力的反复变化磁场或反向磁场中。
• 锤打或是撞击磁性材料。

Degaussing is the process of decreasing or eliminating a remnant magnetic field. It is named after the gauss, a unit of magnetism, which in turn was named after Carl Friedrich Gauss. Due to magnetic hysteresis, it is generally not possible to reduce a magnetic field completely to zero, so degaussing typically induces a very small "known" field referred to as bias. Degaussing was originally applied to reduce ships' magnetic signatures during the Second World War. Degaussing is also used to reduce magnetic fields in CRT monitors and to destroy data held on magnetic data storage.