多输入多输出（Multi-input Multi-output ; MIMO）是一种用来描述多天线无线通信系统的抽象数学模型，能利用发射端的多个天线各自独立发送信号，同时在接收端用多个天线接收并恢复原信息。该技术最早是由马可尼于1908年提出的，他利用多天线来抑制信道衰落（fading）。根据收发两端天线数量，相对于普通的单输入单输出系统（Single-Input Single-Output，SISO），MIMO此类多天线技术尚包含早期所谓的「智能型天线」，亦即单输入多输出系统（Single-Input Multi-Output，SIMO）和多输入单输出系统（Multiple-Input Single-Output，MISO）。

In radio, multiple-input and multiple-output, or MIMO (pronounced as "my-moh" or "me-moh"), is a method for multiplying the capacity of a radio link using multiple transmit and receive antennas to exploit multipath propagation. MIMO has become an essential element of wireless communication standards including IEEE 802.11n (Wi-Fi), IEEE 802.11ac (Wi-Fi), HSPA+ (3G), WiMAX (4G), and Long Term Evolution (4G). More recently, MIMO has been applied to power-line communication for 3-wire installations as part of ITU G.hn standard and HomePlug AV2 specification.