格雷码（循环二进制单位距离码）是任意两个相邻数的代码只有一位二进制数不同的编码，它与奇偶校验码同属可靠性编码。

格雷码（Gray code）是由贝尔实验室的Frank Gray在1940年提出，用于在PCM（脉冲编码调制）方法发送信号时防止出错，并于1953年三月十七日取得美国专利。格雷码是一个数列集合，相邻两数间只有一个比特改变，为无权数码，且格雷码的顺序不是唯一的。

The reflected binary code (RBC), also known as Gray code after Frank Gray, is a binary numeral system where two successive values differ in only one bit (binary digit). The reflected binary code was originally designed to prevent spurious output from electromechanical switches. Today, Gray codes are widely used to facilitate error correction in digital communications such as digital terrestrial television and some cable TV systems.