Rio was a line of digital audio players and related audio products. Its first release, the Rio PMP300 digital music player (also known colloquially as simply the "Diamond Rio"), released by Diamond Multimedia in 1998, was one of the earliest notable and commercially successful devices in its category.^[1] It also became known as the target of an early lawsuit regarding the legality of such devices. Following the PMP300, various music players were released under the Rio brand name by a number of companies until the brand was retired in 2005.

Rio was originally a brand of California based Diamond Multimedia. Rio Audio was best known for producing the Rio PMP300 model that was the impetus for a lawsuit in 1998 by the Recording Industry Association of America.^[2][3] That lawsuit eventually failed,^[2] leading the way for the portable digital music industry to take off.

Diamond Multimedia merged with S3 Graphics in 1999 - the resulting company was renamed SONICblue. Rio, Inc., a subsidiary of SONICblue, was formed in 2000.^[4] The company referred to itself as Rio Digital Audio^[5] - in later years this changed to simply Rio Audio. During this time, Rio's president was Jim Cady.^[6]

On March 21, 2003, SONICblue filed for Chapter 11 bankruptcy protection and then sold off its main product lines; Rio Audio was sold to Japanese firm D&M Holdings,^[7] which owned audio brands such as Denon, forming part of their Digital Networks North America subsidiary. Rio Audio was based in Santa Clara, California.^[8] Its president from that time until March 2004 was Jeffrey Hastings.^[9]

Like some other competitors in the digital audio player business, the Rio brand was unable to compete effectively against Apple's dominant iPod series of audio players.^[10] In August 2005, D&M Holdings announced the discontinuation of its production of audio players, after it had licensed its digital audio software technology to chipmaker SigmaTel the month before.^[11] The Rio brand and trademarks were retained by D&M Holdings.^[12]