无限脉冲响应滤波器，简称IIR数字滤波器（英语：infinite impulse response filter），是数字滤波器的一种。由于无限脉冲响应滤波器中存在反馈回路，因此对于脉冲输入信号的响应是无限延续的。滤波器的任务是通过一定运算关系，改变输入信号的频谱。数字滤波器是利用计算机进程、专用芯片等软、硬件改变量字信号频谱。如果要处理的是仿真信号可以通过A/D在信号形式上进行转换，在利用数字滤波器处理后经过D/A恢复为仿真信号。

Infinite impulse response (IIR) is a property applying to many linear time-invariant systems. Common examples of linear time-invariant systems are most electronic and digital filters. Systems with this property are known as IIR systems or IIR filters, and are distinguished by having an impulse response which does not become exactly zero past a certain point, but continues indefinitely. This is in contrast to a finite impulse response in which the impulse response h(t) does become exactly zero at times t > T for some finite T, thus being of finite duration.