Blu-ray Disc (BD) is a digital optical disc data storage format designed to supersede the DVD format, in that it is capable of storing high-definition video resolution (1080p). The plastic disc is 120 mm in diameter and 1.2 mm thick, the same size as DVDs and CDs. Conventional (pre-BD-XL) Blu-ray Discs contain 25 GB per layer, with dual layer discs (50 GB) being the industry standard for feature-length video discs. Triple layer discs (100 GB) and quadruple layers (128 GB) are available for BD-XL re-writer drives. The name Blu-ray Disc refers to the blue laser used to read the disc, which allows information to be stored at a greater density than is possible with the longer-wavelength red laser used for DVDs. The major application of Blu-ray Discs is as a medium for video material such as feature films and physical distribution of video games for the PlayStation 3, PlayStation 4 and Xbox One. Besides the hardware specifications, Blu-ray Disc is associated with a set of multimedia formats. These formats allow for the option of video and audio to be stored with greater definition than on DVD.

High-definition video may be stored on Blu-ray Discs with up to 1080p resolution (1920×1080 pixels), at up to 60 (59.94) fields per second. Older DVD discs had a maximum resolution of 480p, (NTSC, 720×480 pixels) or 576p, (PAL, 720×576 pixels).

The format was developed by the Blu-ray Disc Association, a group representing makers of consumer electronics, computer hardware, and motion pictures. Sony unveiled the first Blu-ray Disc prototypes in October 2000, and the first prototype player was released in April 2003 in Japan. Afterwards, it continued to be developed until its official release in June 2006. As of June 2008, more than 2,500 Blu-ray Disc titles were available in Australia and the United Kingdom, with 3,500 in the United States and Canada. In Japan, as of July 2010, more than 3,300 titles have been released.

During the high definition optical disc format war, Blu-ray Disc competed with the HD DVD format. Toshiba, the main company that supported HD DVD, conceded in February 2008, releasing its own Blu-ray Disc player in late 2009.