异步传输模式（英文：Asynchronous Transfer Mode，ATM），又叫信元中继。ATM采用电路交换的方式，它以信元（cell）为单位。每个信元长53字节。其中报头占了5字节。

ATM能够比较理想地实现各种QoS，既能够支持有连接的业务，又能支持无连接的业务。是宽带ISDN（B-ISDN）技术的典范。ATM为一种交换技术，在发送数据时，先将数字数据切割成多个固定长度的封包，之后利用光纤或DS1/ DS3发送。到达目的地后，再重新组合。ATM网络可同时将声音、影像及数据集成在一起。针对各种信息型态，提供最佳的传输环境。

Asynchronous Transfer Mode (ATM) is, according to the ATM Forum, "a telecommunications concept defined by ANSI and ITU (formerly CCITT) standards for carriage of a complete range of user traffic, including voice, data, and video signals". ATM was developed to meet the needs of the Broadband Integrated Services Digital Network, as defined in the late 1980s, and designed to unify telecommunication and computer networks. It was designed for a network that must handle both traditional high-throughput data traffic (e.g., file transfers), and real-time, low-latency content such as voice and video. The reference model for ATM approximately maps to the three lowest layers of the ISO-OSI reference model: network layer, data link layer, and physical layer. ATM is a core protocol used over the SONET/SDH backbone of the public switched telephone network (PSTN) and Integrated Services Digital Network (ISDN), but its use is declining in favour of all IP.