分组码（block code），又名块码，是频道编码（channel coding）技术的一种。它在发送端发送的原始消息中，以比特率不会超过频道容量为前提下，加入额外的比特（redundancy），使接收端能够以最小（理论值为0）的错误率解码。

分组码主要的特性为它的密码长度固定（有别于使用变长编码表的霍夫曼编码（Huffman Coding））。一般来说分组码会将包含了k位数的信息字符s，转换到包含n位数的编码字符C(s)；即分组码长度（block length）为n。

分组编码是早期移动通信（mobile communication）系统中，使用的主要频道编码（channel coding）方式。

In coding theory, a block code is any member of the large and important family of error-correcting codes that encode data in blocks. There is a vast number of examples for block codes, many of which have a wide range of practical applications. Block codes are conceptually useful because they allow coding theorists, mathematicians, and computer scientists to study the limitations of all block codes in a unified way. Such limitations often take the form of bounds that relate different parameters of the block code to each other, such as its rate and its ability to detect and correct errors.