HD DVD (short for High-Definition/Density DVD) is a discontinued high-density optical disc format for storing data and high-definition video. Supported principally by Toshiba, HD DVD was envisioned to be the successor to the standard DVD format. However, in February 2008, after a protracted high definition optical disc format war with rival Blu-ray Disc, Toshiba abandoned the format, announcing it would no longer develop or manufacture HD DVD players or drives. However, the HD DVD physical disc specifications (but not the codecs) are still in use as the basis for the CBHD (China Blue High-Definition Disc) formerly called CH-DVD. The HD DVD Promotion Group was dissolved on March 28, 2008.

Because all variants except 3× DVD and HD REC employed a blue laser with a shorter wavelength, HD DVD could store about 3.2 times as much data per layer as its predecessor (maximum capacity: 15 GB per layer instead of 4.7 GB per layer).

In the mid 1990s, commercial HDTV sets started to enter a larger market. However, there was no inexpensive way to record or play back HD content. JVC's D-VHS and Sony's HDCAM formats could store that amount of data, but were neither popular nor well-known. However, it was well known that using lasers with shorter wavelengths would yield optical storage with higher density. Shuji Nakamura invented practical blue laser diodes, however, a lengthy patent lawsuit delayed commercial introduction.