HARQ（Hybrid Automatic Repeat reQuest），混合式自动重送请求，是一种结合FEC（Feed-forward Error Correction，前馈式错误修正）与ARQ方法的技术，透过ACK／NACK，决定是否要重送。

HARQ 是 ARQ的改进，只是在ARQ系统中引入FEC子系统。FEC可用来纠正经常出现的错误图样以减少重传的次数。HARQ应用于HSDPA 与 HSUPA 系统上。

HARQ 的重传基于 ACK/NACK，HARQ 的 ACK/NACK 回报，是以 1比特的信号（signaling）来做快速且频繁地回报，而不是过去ARQ以封包的方式（如 Status Report）回传。在下行链路（Downlink）上支持异步的重传（Asynchronous Retransmissions），上行链路（Uplink）上支持同步的重传（Synchronous Retransmissions）。

Hybrid automatic repeat request (hybrid ARQ or HARQ) is a combination of high-rate forward error-correcting coding and ARQ error-control. In standard ARQ, redundant bits are added to data to be transmitted using an error-detecting (ED) code such as a cyclic redundancy check (CRC). Receivers detecting a corrupted message will request a new message from the sender. In Hybrid ARQ, the original data is encoded with a forward error correction (FEC) code, and the parity bits are either immediately sent along with the message or only transmitted upon request when a receiver detects an erroneous message. The ED code may be omitted when a code is used that can perform both forward error correction (FEC) in addition to error detection, such as a Reed-Solomon code. The FEC code is chosen to correct an expected subset of all errors that may occur, while the ARQ method is used as a fall-back to correct errors that are uncorrectable using only the redundancy sent in the initial transmission. As a result, hybrid ARQ performs better than ordinary ARQ in poor signal conditions, but in its simplest form this comes at the expense of significantly lower throughput in good signal conditions. There is typically a signal quality cross-over point below which simple hybrid ARQ is better, and above which basic ARQ is better.