双倍密度CD（Double Density Compact Disc, DDCD）是一项由Sony开发的光盘科技，使用与CD相同的雷射波长，即780奈米。这个格式描述于彩虹书中的紫皮书规格文档中。

它的直径与CD相同为120公厘，但容量从650MB增大至1.3GB。因为它将原本的1.6微米的轨距缩小至1.1微米，并且把坑洞的最小长度从0.833微米缩小至0.623微米。它有三种格式：一般的DDCD-ROM、可刻录的DDCD-R、可复写的DDCD-RW。这三种格式也可应用在直径80公厘的小光盘形式上。

Double-density compact disc (DDCD) is an optical disc technology developed by Sony using the same laser wavelength as compact disc, namely 780 nm. The format is defined by the Purple Book standard document.

For a 120 mm disc, it doubles the original 650 MB to 1.3 GB capacity of a CD on recordable (DDCD-R) and rewritable (DDCD-RW) discs by narrowing the track pitch from 1.6 to 1.1 micrometers, and shortening the minimum pit length from 0.833 to 0.623 micrometer. The DDCD was also available in read-only format (DDCD-ROM). All three formats existed also in small 80 mm discs.