The 64DD was a magnetic floppy disk drive peripheral for the Nintendo 64 game console developed by Nintendo. It was announced in 1995, prior to the Nintendo 64's 1996 launch, and after numerous delays was released in Japan on December 13, 1999.
　The "64" references both the Nintendo 64 console and the 64MB storage capacity of the disks, and "DD" is short for "disk drive" or "dynamic drive". Most games once planned for 64DD were released as standard Nintendo 64 games, ported to other consoles such as the GameCube, or canceled.

　Plugging into the extension port on the underside of the console, the 64DD allows the Nintendo 64 to use proprietary 64MB magnetic disks for expanded and rewritable data storage, a real-time clock for persistent game world design, and a standard font and audio library for further storage efficiency. Its games and hardware accessories let the user create movies, characters, and animations to use within various other games and shared online. The system could connect to the Internet through a dedicated online service, Randnet, for e-commerce, online gaming, and media sharing.
Describing it as "the first writable bulk data storage device for a modern video game console", Nintendo designed the 64DD as an enabling technology platform for the development of new genres of games and applications, several of which were in development for several years. Only ten disks had been released and Randnet had 15,000 subscribers, when the 64DD was discontinued in February 2001. It was a commercial failure, with at least 15,000 total units sold, and was never released outside Japan.