The double-density compact disc (DDCD) is an optical disc technology developed by Sony using the same laser wavelength as a compact disc, namely 780 nm. The format is defined by the Purple Book standard document. Unlike the compact-disc technology it is based on, DDCD was designed exclusively for data, with no audio capabilities.

For a 12 cm 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 micrometers. The DDCD was also available in read-only format (DDCD-ROM). The specification allowed for both 12 cm and 8 cm discs, although it appears no 8 cm media was ever released.

The technology, released years after rewritable DVD technology, failed to acquire significant market share. The only DDCD recorder introduced was the Sony CRX200E. While the initial launch price of the drive and the disc ($249 and $2-3 respectively) was lower than the prices of DVD-RW drives and media ($1000 and $10 respectively), an 85% increase in storage compared to the standard 700 MB CDs was not enough to entice customers. A similar technology, however, was used in the GD-ROM discs primarily used for Sega Dreamcast software. DVD offered a significantly higher capacity - nearly four times more than DDCD-R with 4.7 GB on single layer discs and six and a half times more with 8.5 GB on double layer discs and would drop significantly in cost in the years after DDCD's launch.

The DDCD technology was marked as 'legacy' in the 2006-edition of the SCSI Multimedia Commands set (MMC).